diff --git a/chronos.nimble b/chronos.nimble
index a4638314..55196c08 100644
--- a/chronos.nimble
+++ b/chronos.nimble
@@ -1,5 +1,5 @@
 packageName   = "chronos"
-version       = "2.2.1"
+version       = "2.2.2"
 author        = "Status Research & Development GmbH"
 description   = "Chronos"
 license       = "Apache License 2.0 or MIT"
@@ -9,26 +9,45 @@ skipDirs      = @["tests"]
 
 requires "nim > 0.18.0"
 
-task test, "Run all tests":
-  for tfile in @[
-      "testsync",
-      "testsoon",
-      "testtime",
-      "testfut",
-      "testsignal",
-      "testaddress",
-      "testdatagram",
-      "teststream",
-      "testserver",
-      "testbugs",
-    ]:
-    for cmd in @[
-        "nim c -r -d:useSysAssert -d:useGcAssert tests/" & tfile,
-        "nim c -r tests/" & tfile,
-        #"nim c -r --gc:markAndSweep tests/" & tfile,
-        "nim c -r -d:release tests/" & tfile
-      ]:
-      echo "\n" & cmd
-      exec cmd
-      rmFile("tests/" & tfile.toExe())
+import ospaths
 
+task test, "Run all tests":
+
+  var testFiles = @[
+    "testsync",
+    "testsoon",
+    "testtime",
+    "testfut",
+    "testsignal",
+    "testaddress",
+    "testdatagram",
+    "teststream",
+    "testserver",
+    "testbugs",
+  ]
+
+  var testCommands = @[
+    "nim c -r -d:useSysAssert -d:useGcAssert",
+    "nim c -r",
+    "nim c -r -d:release"
+  ]
+
+  var timerCommands = @[
+    " -d:asyncTimer=system",
+    " -d:asyncTimer=mono"
+  ]
+
+  for tfile in testFiles:
+    if tfile == "testtime":
+      for cmd in testCommands:
+        for def in timerCommands:
+          var commandLine = (cmd & def & " tests") / tfile
+          echo "\n" & commandLine
+          exec commandLine
+          rmFile("tests" / tfile.toExe())
+    else:
+      for cmd in testCommands:
+        var commandLine = (cmd & " tests") / tfile
+        echo "\n" & commandLine
+        exec commandLine
+        rmFile("tests" / tfile.toExe())
diff --git a/chronos/asyncloop.nim b/chronos/asyncloop.nim
index 1eeed641..da1e1433 100644
--- a/chronos/asyncloop.nim
+++ b/chronos/asyncloop.nim
@@ -165,6 +165,13 @@ export asyncfutures2, timer
 
 # TODO: Check if yielded future is nil and throw a more meaningful exception
 
+when defined(windows):
+  import winlean, sets, hashes
+else:
+  import selectors
+  from posix import EINTR, EAGAIN, EINPROGRESS, EWOULDBLOCK, MSG_PEEK,
+                    MSG_NOSIGNAL
+
 type
   AsyncError* = object of Exception
     ## Generic async exception
@@ -172,7 +179,7 @@ type
     ## Timeout exception
 
   TimerCallback* = object
-    finishAt*: uint64
+    finishAt*: Moment
     function*: AsyncCallback
 
   PDispatcherBase = ref object of RootRef
@@ -188,6 +195,24 @@ proc initCallSoonProc() =
   if asyncfutures2.getCallSoonProc().isNil:
     asyncfutures2.setCallSoonProc(callSoon)
 
+func getAsyncTimestamp*(a: Duration): auto {.inline.} =
+  ## Return rounded up value of duration with milliseconds resolution.
+  ##
+  ## This function also take care on int32 overflow, because Linux and Windows
+  ## accepts signed 32bit integer as timeout.
+  let milsec = Millisecond.nanoseconds()
+  let nansec = a.nanoseconds()
+  var res = nansec div milsec
+  let mid = nansec mod milsec
+  when defined(windows):
+    res = min(cast[int64](high(int32) - 1), res)
+    result = cast[DWORD](res)
+    result += DWORD(min(1'i32, cast[int32](mid)))
+  else:
+    res = min(cast[int64](high(int32) - 1), res)
+    result = cast[int32](res)
+    result += min(1, cast[int32](mid))
+
 template processTimersGetTimeout(loop, timeout: untyped) =
   var count = len(loop.timers)
   if count > 0:
@@ -199,10 +224,7 @@ template processTimersGetTimeout(loop, timeout: untyped) =
       loop.callbacks.addLast(loop.timers.pop().function)
       dec(count)
     if count > 0:
-      when defined(windows):
-        timeout = DWORD(lastFinish - curTime)
-      else:
-        timeout = int(lastFinish - curTime)
+      timeout = (lastFinish - curTime).getAsyncTimestamp()
 
   if timeout == 0:
     if len(loop.callbacks) == 0:
@@ -215,7 +237,7 @@ template processTimersGetTimeout(loop, timeout: untyped) =
       timeout = 0
 
 template processTimers(loop: untyped) =
-  var curTime = fastEpochTime()
+  var curTime = Moment.now()
   var count = len(loop.timers)
   if count > 0:
     while count > 0:
@@ -238,7 +260,6 @@ template processCallbacks(loop: untyped) =
       callable.function(callable.udata)
 
 when defined(windows) or defined(nimdoc):
-  import winlean, sets, hashes
   type
     WSAPROC_TRANSMITFILE = proc(hSocket: SocketHandle, hFile: Handle,
                                 nNumberOfBytesToWrite: DWORD,
@@ -316,7 +337,7 @@ when defined(windows) or defined(nimdoc):
   proc poll*() =
     ## Perform single asynchronous step.
     let loop = getGlobalDispatcher()
-    var curTime = fastEpochTime()
+    var curTime = Moment.now()
     var curTimeout = DWORD(0)
 
     # Moving expired timers to `loop.callbacks` and calculate timeout
@@ -328,8 +349,10 @@ when defined(windows) or defined(nimdoc):
     var customOverlapped: PtrCustomOverlapped
 
     let res = getQueuedCompletionStatus(
-      loop.ioPort, addr lpNumberOfBytesTransferred, addr lpCompletionKey,
-      cast[ptr POVERLAPPED](addr customOverlapped), curTimeout).bool
+      loop.ioPort, addr lpNumberOfBytesTransferred,
+      addr lpCompletionKey, cast[ptr POVERLAPPED](addr customOverlapped),
+      curTimeout).bool
+
     if res:
       customOverlapped.data.bytesCount = lpNumberOfBytesTransferred
       customOverlapped.data.errCode = OSErrorCode(-1)
@@ -428,9 +451,6 @@ when defined(windows) or defined(nimdoc):
     return fd in disp.handles
 
 else:
-  import selectors
-  from posix import EINTR, EAGAIN, EINPROGRESS, EWOULDBLOCK, MSG_PEEK,
-                    MSG_NOSIGNAL
   type
     AsyncFD* = distinct cint
 
@@ -611,7 +631,7 @@ else:
   proc poll*() =
     ## Perform single asynchronous step.
     let loop = getGlobalDispatcher()
-    var curTime = fastEpochTime()
+    var curTime = Moment.now()
     var curTimeout = 0
 
     when ioselSupportedPlatform:
@@ -655,7 +675,7 @@ else:
   proc initAPI() =
     discard getGlobalDispatcher()
 
-proc addTimer*(at: uint64, cb: CallbackFunc, udata: pointer = nil) =
+proc addTimer*(at: Moment, cb: CallbackFunc, udata: pointer = nil) =
   ## Arrange for the callback ``cb`` to be called at the given absolute
   ## timestamp ``at``. You can also pass ``udata`` to callback.
   let loop = getGlobalDispatcher()
@@ -663,7 +683,11 @@ proc addTimer*(at: uint64, cb: CallbackFunc, udata: pointer = nil) =
                           function: AsyncCallback(function: cb, udata: udata))
   loop.timers.push(tcb)
 
-proc removeTimer*(at: uint64, cb: CallbackFunc, udata: pointer = nil) =
+proc addTimer*(at: int64, cb: CallbackFunc, udata: pointer = nil) {.
+     inline, deprecated: "Use addTimer(Duration, cb, udata)".} =
+  addTimer(Moment.init(at, Millisecond), cb, udata)
+
+proc removeTimer*(at: Moment, cb: CallbackFunc, udata: pointer = nil) =
   ## Remove timer callback ``cb`` with absolute timestamp ``at`` from waiting
   ## queue.
   let loop = getGlobalDispatcher()
@@ -677,18 +701,25 @@ proc removeTimer*(at: uint64, cb: CallbackFunc, udata: pointer = nil) =
   if index != -1:
     loop.timers.del(index)
 
-proc sleepAsync*(ms: int): Future[void] =
+proc removeTimer*(at: int64, cb: CallbackFunc, udata: pointer = nil) {.
+     inline, deprecated: "Use removeTimer(Duration, cb, udata)".} =
+  removeTimer(Moment.init(at, Millisecond), cb, udata)
+
+proc sleepAsync*(ms: Duration): Future[void] =
   ## Suspends the execution of the current async procedure for the next
   ## ``ms`` milliseconds.
   var retFuture = newFuture[void]("sleepAsync")
   proc completion(data: pointer) =
     if not retFuture.finished:
       retFuture.complete()
-  addTimer(fastEpochTime() + uint64(ms),
-           completion, cast[pointer](retFuture))
+  addTimer(Moment.fromNow(ms), completion, cast[pointer](retFuture))
   return retFuture
 
-proc withTimeout*[T](fut: Future[T], timeout: int): Future[bool] =
+proc sleepAsync*(ms: int): Future[void] {.
+     inline, deprecated: "Use sleepAsync(Duration)".} =
+  result = sleepAsync(ms.milliseconds())
+
+proc withTimeout*[T](fut: Future[T], timeout: Duration): Future[bool] =
   ## Returns a future which will complete once ``fut`` completes or after
   ## ``timeout`` milliseconds has elapsed.
   ##
@@ -704,11 +735,15 @@ proc withTimeout*[T](fut: Future[T], timeout: int): Future[bool] =
       else:
         if not retFuture.finished:
           retFuture.complete(true)
-  addTimer(fastEpochTime() + uint64(timeout), continuation, nil)
+  addTimer(Moment.fromNow(timeout), continuation, nil)
   fut.addCallback(continuation)
   return retFuture
 
-proc wait*[T](fut: Future[T], timeout = -1): Future[T] =
+proc withTimeout*[T](fut: Future[T], timeout: int): Future[bool] {.
+     inline, deprecated: "Use withTimeout(Future[T], Duration)".} =
+  result = withTimeout(fut, timeout.milliseconds())
+
+proc wait*[T](fut: Future[T], timeout = InfiniteDuration): Future[T] =
   ## Returns a future which will complete once future ``fut`` completes
   ## or if timeout of ``timeout`` milliseconds has been expired.
   ##
@@ -726,9 +761,9 @@ proc wait*[T](fut: Future[T], timeout = -1): Future[T] =
             retFuture.fail(fut.error)
           else:
             retFuture.complete(fut.read())
-  if timeout == -1:
+  if timeout.isInfinite():
     retFuture = fut
-  elif timeout == 0:
+  elif timeout.isZero():
     if fut.finished:
       if fut.failed:
         retFuture.fail(fut.error)
@@ -737,10 +772,19 @@ proc wait*[T](fut: Future[T], timeout = -1): Future[T] =
     else:
       retFuture.fail(newException(AsyncTimeoutError, ""))
   else:
-    addTimer(fastEpochTime() + uint64(timeout), continuation, nil)
+    addTimer(Moment.fromNow(timeout), continuation, nil)
     fut.addCallback(continuation)
   return retFuture
 
+proc wait*[T](fut: Future[T], timeout = -1): Future[T] {.
+     inline, deprecated: "Use wait(Future[T], Duration)".} =
+  if timeout == -1:
+    wait(fut, InfiniteDuration)
+  elif timeout == 0:
+    wait(fut, ZeroDuration)
+  else:
+    wait(fut, timeout.milliseconds())
+
 include asyncmacro2
 
 proc callSoon(cbproc: CallbackFunc, data: pointer = nil) =
diff --git a/chronos/timer.nim b/chronos/timer.nim
index 84105049..62f9034d 100644
--- a/chronos/timer.nim
+++ b/chronos/timer.nim
@@ -8,45 +8,437 @@
 #    Apache License, version 2.0, (LICENSE-APACHEv2)
 #                MIT license (LICENSE-MIT)
 
-
 ## This module implements cross-platform system timer with
 ## milliseconds resolution.
+##
+## Timer supports two types of clocks:
+## ``system`` uses the most fast OS primitive to obtain wall clock time.
+## ``mono`` uses monotonic clock time (default).
+##
+## ``system`` clock is affected by discontinuous jumps in the system time. This
+## clock is significantly faster then ``mono`` clock in most of the cases.
+##
+## ``mono`` clock is not affected by discontinuous jumps in the system time.
+## This clock is slower then ``system`` clock.
+##
+## You can specify which timer you want to use ``-d:asyncTimer=<system/mono>``.
+const asyncTimer* {.strdefine.} = "mono"
 
 when defined(windows):
+  from winlean import DWORD
 
-  from winlean import DWORD, getSystemTimeAsFileTime, FILETIME
+  when asyncTimer == "system":
+    from winlean import getSystemTimeAsFileTime, FILETIME
 
-  proc fastEpochTime*(): uint64 {.inline.} =
-    var t: FILETIME
-    getSystemTimeAsFileTime(t)
-    result = ((uint64(t.dwHighDateTime) shl 32) or
-              uint64(t.dwLowDateTime)) div 10_000
+    proc fastEpochTime*(): uint64 {.
+         inline, deprecated: "Use Moment.now()".} =
+      ## Timer resolution is millisecond.
+      var t: FILETIME
+      getSystemTimeAsFileTime(t)
+      result = ((cast[uint64](t.dwHighDateTime) shl 32) or
+                 cast[uint64](t.dwLowDateTime)) div 10_000
+
+    proc fastEpochTimeNano(): uint64 {.inline.} =
+      ## Timer resolution is nanosecond.
+      var t: FILETIME
+      getSystemTimeAsFileTime(t)
+      result = ((cast[uint64](t.dwHighDateTime) shl 32) or
+                 cast[uint64](t.dwLowDateTime)) * 100
+
+  else:
+    proc QueryPerformanceCounter(res: var uint64) {.
+      importc: "QueryPerformanceCounter", stdcall, dynlib: "kernel32".}
+    proc QueryPerformanceFrequency(res: var uint64) {.
+      importc: "QueryPerformanceFrequency", stdcall, dynlib: "kernel32".}
+
+    var queryFrequencyM: uint64
+    var queryFrequencyN: uint64
+
+    proc fastEpochTimeNano(): uint64 {.inline.} =
+      ## Procedure's resolution is nanosecond.
+      var res: uint64
+      QueryPerformanceCounter(res)
+      result = res * queryFrequencyN
+
+    proc fastEpochTime*(): uint64 {.
+         inline, deprecated: "Use Moment.now()".} =
+      ## Procedure's resolution is millisecond.
+      var res: uint64
+      QueryPerformanceCounter(res)
+      result = res div queryFrequencyM
+
+    proc setupQueryFrequence() =
+      var freq: uint64
+      QueryPerformanceFrequency(freq)
+      if freq < 1000:
+        queryFrequencyM = freq
+      else:
+        queryFrequencyM = freq div 1_000
+      queryFrequencyN = 1_000_000_000'u64 div freq
+
+    setupQueryFrequence()
 
 elif defined(macosx):
 
-  from posix import Timeval
+  when asyncTimer == "system":
+    from posix import Timeval
 
-  proc posix_gettimeofday(tp: var Timeval, unused: pointer = nil) {.
-    importc: "gettimeofday", header: "<sys/time.h>".}
+    proc posix_gettimeofday(tp: var Timeval, unused: pointer = nil) {.
+      importc: "gettimeofday", header: "<sys/time.h>".}
 
-  proc fastEpochTime*(): uint64 {.inline.} =
-    var t: Timeval
-    posix_gettimeofday(t)
-    result = (uint64(t.tv_sec) * 1_000 + uint64(t.tv_usec) div 1_000)
+    proc fastEpochTime*(): uint64 {.
+         inline, deprecated: "Use Moment.now()".} =
+      ## Procedure's resolution is millisecond.
+      var t: Timeval
+      posix_gettimeofday(t)
+      result = (cast[uint64](t.tv_sec) * 1_000 +
+                cast[uint64](t.tv_usec) div 1_000)
+
+    proc fastEpochTimeNano(): uint64 {.inline.} =
+      ## Procedure's resolution is nanosecond.
+      var t: Timeval
+      posix_gettimeofday(t)
+      result = (cast[uint64](t.tv_sec) * 1_000_000_000 +
+                cast[uint64](t.tv_usec) * 1_000)
+  else:
+    from posix import clock_gettime, Timespec, CLOCK_MONOTONIC
+
+    proc fastEpochTime*(): uint64 {.
+         inline, deprecated: "Use Moment.now()".} =
+      ## Procedure's resolution is millisecond.
+      var t: Timespec
+      discard clock_gettime(CLOCK_MONOTONIC, t)
+      result = ((cast[uint64](t.tv_sec) * 1_000) +
+                (cast[uint64](t.tv_nsec) div 1_000_000))
+
+    proc fastEpochTimeNano(): uint64 {.inline.} =
+      ## Procedure's resolution is nanosecond.
+      var t: Timespec
+      discard clock_gettime(CLOCK_MONOTONIC, t)
+      result = cast[uint64](t.tv_sec) * 1_000_000_000'u64 +
+               cast[uint64](t.tv_nsec)
 
 elif defined(posix):
+  from posix import clock_gettime, Timespec, CLOCK_REALTIME, CLOCK_MONOTONIC
 
-  from posix import clock_gettime, Timespec, CLOCK_REALTIME
+  when asyncTimer == "system":
+    proc fastEpochTime*(): uint64 {.
+         inline, deprecated: "Use Moment.now()".} =
+      ## Procedure's resolution is millisecond.
+      var t: Timespec
+      discard clock_gettime(CLOCK_REALTIME, t)
+      result = (cast[uint64](t.tv_sec) * 1_000 +
+                (cast[uint64](t.tv_nsec) div 1_000_000))
 
-  proc fastEpochTime*(): uint64 {.inline.} =
-    var t: Timespec
-    discard clock_gettime(CLOCK_REALTIME, t)
-    result = (uint64(t.tv_sec) * 1_000 + uint64(t.tv_nsec) div 1_000_000)
+    proc fastEpochTimeNano(): uint64 {.inline.} =
+      ## Procedure's resolution is nanosecond.
+      var t: Timespec
+      discard clock_gettime(CLOCK_REALTIME, t)
+      result = cast[uint64](t.tv_sec) * 1_000_000_000'u64 +
+               cast[uint64](t.tv_nsec)
+
+  else:
+    proc fastEpochTime*(): uint64 {.
+         inline, deprecated: "Use Moment.now()".} =
+      ## Procedure's resolution is millisecond.
+      var t: Timespec
+      discard clock_gettime(CLOCK_MONOTONIC, t)
+      result = (cast[uint64](t.tv_sec) * 1_000 +
+                (cast[uint64](t.tv_nsec) div 1_000_000))
+
+    proc fastEpochTimeNano(): uint64 {.inline.} =
+      ## Procedure's resolution is nanosecond.
+      var t: Timespec
+      discard clock_gettime(CLOCK_MONOTONIC, t)
+      result = cast[uint64](t.tv_sec) * 1_000_000_000'u64 +
+               cast[uint64](t.tv_nsec)
 
 elif defined(nimdoc):
 
-  proc fastEpochTime*(): uint64
+  proc fastEpochTime*(): uint64 {.deprecated: "Use Moment.now()".}
     ## Returns system's timer in milliseconds.
 
 else:
   error("Sorry, your operation system is not yet supported!")
+
+type
+  Moment* = object
+    ## A Moment in time. Its value has no direct meaning, but can be compared
+    ## with other Moments. Moments are captured using a monotonically
+    ## non-decreasing clock (by default).
+    value: int64
+
+  Duration* = object
+    ## A Duration is the interval between to points in time.
+    value: int64
+
+when sizeof(int) == 4:
+  type SomeIntegerI64* = SomeSignedInt|uint|uint8|uint16|uint32
+else:
+  type SomeIntegerI64* = SomeSignedInt|uint8|uint16|uint32
+
+func `+`*(a: Duration, b: Duration): Duration {.inline.} =
+  ## Duration + Duration = Duration
+  result.value = a.value + b.value
+
+func `+`*(a: Duration, b: Moment): Moment {.inline.} =
+  ## Duration + Moment = Moment
+  result.value = a.value + b.value
+
+func `+`*(a: Moment, b: Duration): Moment {.inline.} =
+  ## Moment + Duration = Moment
+  result.value = a.value + b.value
+
+func `+=`*(a: var Moment, b: Duration) {.inline.} =
+  ## Moment += Duration
+  a.value += b.value
+
+func `+=`*(a: var Duration, b: Duration) {.inline.} =
+  ## Duration += Duration
+  a.value += b.value
+
+func `-`*(a, b: Moment): Duration {.inline.} =
+  ## Moment - Moment = Duration
+  ##
+  ## Note: Duration can't be negative.
+  result.value = if a.value >= b.value: a.value - b.value else: 0'i64
+
+func `-`*(a: Moment, b: Duration): Moment {.inline.} =
+  ## Moment - Duration = Moment
+  ##
+  ## Note: Moment can be negative
+  result.value = a.value - b.value
+
+func `-`*(a: Duration, b: Duration): Duration {.inline.} =
+  ## Duration - Duration = Duration
+  ##
+  ## Note: Duration can't be negative.
+  result.value = if a.value >= b.value: a.value - b.value else: 0'i64
+
+func `-=`*(a: var Duration, b: Duration): Duration {.inline.} =
+  ## Duration -= Duration
+  a.value = if a.value >= b.value: a.value - b.value else: 0'i64
+
+func `-=`*(a: var Moment, b: Duration): Moment {.inline.} =
+  ## Moment -= Duration
+  a.value -= b.value
+
+func `==`*(a, b: Duration): bool {.inline.} =
+  ## Returns ``true`` if ``a`` equal to ``b``.
+  result = (a.value == b.value)
+
+func `==`*(a, b: Moment): bool {.inline.} =
+  ## Returns ``true`` if ``a`` equal to ``b``.
+  result = (a.value == b.value)
+
+func `<`*(a, b: Duration): bool {.inline.} =
+  ## Returns ``true`` if ``a`` less then ``b``.
+  result = (a.value < b.value)
+
+func `<`*(a, b: Moment): bool {.inline.} =
+  ## Returns ``true`` if ``a`` less then ``b``.
+  result = (a.value < b.value)
+
+func `<=`*(a, b: Duration): bool {.inline.} =
+  ## Returns ``true`` if ``a`` less or equal ``b``.
+  result = (a.value <= b.value)
+
+func `<=`*(a, b: Moment): bool {.inline.} =
+  ## Returns ``true`` if ``a`` less or equal ``b``.
+  result = (a.value <= b.value)
+
+func `>`*(a, b: Duration): bool {.inline.} =
+  ## Returns ``true`` if ``a`` bigger then ``b``.
+  result = (a.value > b.value)
+
+func `>`*(a, b: Moment): bool {.inline.} =
+  ## Returns ``true`` if ``a`` bigger then ``b``.
+  result = (a.value > b.value)
+
+func `>=`*(a, b: Duration): bool {.inline.} =
+  ## Returns ``true`` if ``a`` bigger or equal ``b``.
+  result = (a.value >= b.value)
+
+func `>=`*(a, b: Moment): bool {.inline.} =
+  ## Returns ``true`` if ``a`` bigger or equal ``b``.
+  result = (a.value >= b.value)
+
+func `*`*(a: Duration, b: SomeIntegerI64): Duration {.inline.} =
+  ## Returns Duration multiplied by scalar integer.
+  result.value = a.value * cast[int64](b)
+
+func `*`*(a: SomeIntegerI64, b: Duration): Duration {.inline.} =
+  ## Returns Duration multiplied by scalar integer.
+  result.value = cast[int64](a) * b.value
+
+func `div`*(a: Duration, b: SomeIntegerI64): Duration {.inline.} =
+  ## Returns Duration which is result of dividing a Duration by scalar integer.
+  result.value = a.value div cast[int64](b)
+
+const
+  Nanosecond* = Duration(value: 1'i64)
+  Microsecond* = Nanosecond * 1_000'i64
+  Millisecond* = Microsecond * 1_000'i64
+  Second* = Millisecond * 1_000'i64
+  Minute* = Second * 60'i64
+  Hour* = Minute * 60'i64
+  Day* = Hour * 24'i64
+  Week* = Day * 7'i64
+
+  ZeroDuration* = Duration(value: 0'i64)
+  InfiniteDuration* = Duration(value: high(int64))
+
+func nanoseconds*(v: SomeIntegerI64): Duration {.inline.} =
+  ## Initialize Duration with nanoseconds value ``v``.
+  result.value = cast[int64](v)
+
+func microseconds*(v: SomeIntegerI64): Duration {.inline.} =
+  ## Initialize Duration with microseconds value ``v``.
+  result.value = cast[int64](v) * Microsecond.value
+
+func milliseconds*(v: SomeIntegerI64): Duration {.inline.} =
+  ## Initialize Duration with milliseconds value ``v``.
+  result.value = cast[int64](v) * Millisecond.value
+
+func seconds*(v: SomeIntegerI64): Duration {.inline.} =
+  ## Initialize Duration with seconds value ``v``.
+  result.value = cast[int64](v) * Second.value
+
+func minutes*(v: SomeIntegerI64): Duration {.inline.} =
+  ## Initialize Duration with minutes value ``v``.
+  result.value = Minute.value * cast[int64](v)
+
+func hours*(v: SomeIntegerI64): Duration {.inline.} =
+  ## Initialize Duration with hours value ``v``.
+  result.value = cast[int64](v) * Hour.value
+
+func days*(v: SomeIntegerI64): Duration {.inline.} =
+  ## Initialize Duration with days value ``v``.
+  result.value = cast[int64](v) * Day.value
+
+func weeks*(v: SomeIntegerI64): Duration {.inline.} =
+  ## Initialize Duration with weeks value ``v``.
+  result.value = cast[int64](v) * Week.value
+
+func nanoseconds*(v: Duration): int64 {.inline.} =
+  ## Round Duration ``v`` to nanoseconds.
+  result = v.value
+
+func microseconds*(v: Duration): int64 {.inline.} =
+  ## Round Duration ``v`` to microseconds.
+  result = v.value div Microsecond.value
+
+func milliseconds*(v: Duration): int64 {.inline.} =
+  ## Round Duration ``v`` to milliseconds.
+  result = v.value div Millisecond.value
+
+func seconds*(v: Duration): int64 {.inline.} =
+  ## Round Duration ``v`` to seconds.
+  result = v.value div Second.value
+
+func minutes*(v: Duration): int64 {.inline.} =
+  ## Round Duration ``v`` to minutes.
+  result = v.value div Minute.value
+
+func hours*(v: Duration): int64 {.inline.} =
+  ## Round Duration ``v`` to hours.
+  result = v.value div Hour.value
+
+func days*(v: Duration): int64 {.inline.} =
+  ## Round Duration ``v`` to days.
+  result = v.value div Day.value
+
+func weeks*(v: Duration): int64 {.inline.} =
+  ## Round Duration ``v`` to weeks.
+  result = v.value div Week.value
+
+func nanos*(v: SomeIntegerI64): Duration {.inline.} =
+  result = nanoseconds(v)
+
+func micros*(v: SomeIntegerI64): Duration {.inline.} =
+  result = microseconds(v)
+
+func millis*(v: SomeIntegerI64): Duration {.inline.} =
+  result = milliseconds(v)
+
+func secs*(v: SomeIntegerI64): Duration {.inline.} =
+  result = seconds(v)
+
+func nanos*(v: Duration): int64 {.inline.} =
+  result = nanoseconds(v)
+
+func micros*(v: Duration): int64 {.inline.} =
+  result = microseconds(v)
+
+func millis*(v: Duration): int64 {.inline.} =
+  result = milliseconds(v)
+
+func secs*(v: Duration): int64 {.inline.} =
+  result = seconds(v)
+
+func `$`*(a: Duration): string {.inline.} =
+  ## Returns string representation of Duration ``a`` as nanoseconds value.
+  var v = a.value
+  if v >= Week.value:
+    result = $(v div Week.value) & "w"
+    v = v mod Week.value
+  if v >= Day.value:
+    result &= $(v div Day.value) & "d"
+    v = v mod Day.value
+  if v >= Hour.value:
+    result &= $(v div Hour.value) & "h"
+    v = v mod Hour.value
+  if v >= Minute.value:
+    result &= $(v div Minute.value) & "m"
+    v = v mod Minute.value
+  if v >= Second.value:
+    result &= $(v div Second.value) & "s"
+    v = v mod Second.value
+  if v >= Millisecond.value:
+    result &= $(v div Millisecond.value) & "ms"
+    v = v mod Millisecond.value
+  if v >= Microsecond.value:
+    result &= $(v div Microsecond.value) & "us"
+    v = v mod Microsecond.value
+  if v >= Nanosecond.value:
+    result &= $(v div Nanosecond.value) & "ns"
+
+func `$`*(a: Moment): string {.inline.} =
+  ## Returns string representation of Moment ``a`` as nanoseconds value.
+  result = $(a.value)
+  result.add("ns")
+
+func isZero*(a: Duration): bool {.inline.} =
+  ## Returns ``true`` if Duration ``a`` is ``0``.
+  result = (a.value == 0)
+
+func isInfinite*(a: Duration): bool {.inline.} =
+  ## Returns ``true`` if Duration ``a`` is infinite.
+  result = (a.value == InfiniteDuration.value)
+
+proc now*(t: typedesc[Moment]): Moment {.inline.} =
+  ## Returns current moment in time as Moment.
+  result.value = cast[int64](fastEpochTimeNano())
+
+func init*(t: typedesc[Moment], value: int64, precision: Duration): Moment =
+  ## Initialize Moment with absolute time value ``value`` with precision
+  ## ``precision``.
+  result.value = value * precision.value
+
+proc fromNow*(t: typedesc[Moment], a: Duration): Moment {.inline.} =
+  ## Returns moment in time which is equal to current moment + Duration.
+  result = Moment.now() + a
+
+when defined(posix):
+  from posix import Time, Suseconds, Timeval, Timespec
+
+  func toTimeval*(a: Duration): Timeval =
+    ## Convert Duration ``a`` to ``Timeval`` object.
+    let m = a.value mod Second.value
+    result.tv_sec = cast[Time](a.value div Second.value)
+    result.tv_usec = cast[Suseconds](m div Microsecond.value)
+
+  func toTimespec*(a: Duration): Timespec =
+    ## Convert Duration ``a`` to ``Timespec`` object.
+    result.tv_sec = cast[Time](a.value div Second.value)
+    result.tv_nsec = cast[int](a.value mod Second.value)
diff --git a/chronos/transports/stream.nim b/chronos/transports/stream.nim
index 1dd81e36..5165301f 100644
--- a/chronos/transports/stream.nim
+++ b/chronos/transports/stream.nim
@@ -582,7 +582,7 @@ when defined(windows):
         if pipeHandle == INVALID_HANDLE_VALUE:
           let err = osLastError()
           if int32(err) == ERROR_PIPE_BUSY:
-            addTimer(fastEpochTime() + 50, pipeContinuation, nil)
+            addTimer(Moment.fromNow(50.milliseconds), pipeContinuation, nil)
           else:
             retFuture.fail(getTransportOsError(err))
         else:
diff --git a/tests/testdatagram.nim b/tests/testdatagram.nim
index f2b7997f..955ddec6 100644
--- a/tests/testdatagram.nim
+++ b/tests/testdatagram.nim
@@ -444,7 +444,7 @@ proc testConnReset(): Future[bool] {.async.} =
   var dgram2 = newDatagramTransport(clientMark)
   var data = "MESSAGE"
   asyncCheck dgram2.sendTo(ta, data)
-  await sleepAsync(1000)
+  await sleepAsync(2000.milliseconds)
   result = (counter == 0)
   dgram2.close()
   await dgram2.join()
diff --git a/tests/testfut.nim b/tests/testfut.nim
index bafdbfe2..53b715ef 100644
--- a/tests/testfut.nim
+++ b/tests/testfut.nim
@@ -10,7 +10,7 @@ import unittest
 import ../chronos
 
 proc testFuture1(): Future[int] {.async.} =
-  await sleepAsync(100)
+  await sleepAsync(1.milliseconds)
 
 proc testFuture2(): Future[int] {.async.} =
   return 1
@@ -18,11 +18,14 @@ proc testFuture2(): Future[int] {.async.} =
 proc testFuture3(): Future[int] {.async.} =
   result = await testFuture2()
 
+proc testFuture100(): Future[int] {.async.} =
+  await sleepAsync(100.milliseconds)
+
 proc testFuture4(): Future[int] {.async.} =
   ## Test for not immediately completed future and timeout = -1
   result = 0
   try:
-    var res = await wait(testFuture1(), -1)
+    var res = await wait(testFuture1(), InfiniteDuration)
     result = 1
   except:
     result = 0
@@ -33,7 +36,7 @@ proc testFuture4(): Future[int] {.async.} =
   ## Test for immediately completed future and timeout = -1
   result = 0
   try:
-    var res = await wait(testFuture2(), -1)
+    var res = await wait(testFuture2(), InfiniteDuration)
     result = 2
   except:
     result = 0
@@ -44,7 +47,7 @@ proc testFuture4(): Future[int] {.async.} =
   ## Test for not immediately completed future and timeout = 0
   result = 0
   try:
-    var res = await wait(testFuture1(), 0)
+    var res = await wait(testFuture1(), 0.milliseconds)
   except AsyncTimeoutError:
     result = 3
 
@@ -54,7 +57,7 @@ proc testFuture4(): Future[int] {.async.} =
   ## Test for immediately completed future and timeout = 0
   result = 0
   try:
-    var res = await wait(testFuture2(), 0)
+    var res = await wait(testFuture2(), 0.milliseconds)
     result = 4
   except:
     result = 0
@@ -65,7 +68,7 @@ proc testFuture4(): Future[int] {.async.} =
   ## Test for future which cannot be completed in timeout period
   result = 0
   try:
-    var res = await wait(testFuture1(), 50)
+    var res = await wait(testFuture100(), 50.milliseconds)
   except AsyncTimeoutError:
     result = 5
 
@@ -74,7 +77,7 @@ proc testFuture4(): Future[int] {.async.} =
 
   ## Test for future which will be completed before timeout exceeded.
   try:
-    var res = await wait(testFuture1(), 300)
+    var res = await wait(testFuture100(), 500.milliseconds)
     result = 6
   except:
     result = -6
@@ -83,6 +86,8 @@ proc test1(): bool =
   var fut = testFuture1()
   poll()
   poll()
+  if not fut.finished:
+    poll()
   result = fut.finished
 
 proc test2(): bool =
@@ -138,106 +143,106 @@ proc testAllVarargs(): int =
   var completedFutures = 0
 
   proc vlient1() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
 
   proc vlient2() {.async.} =
-    await sleepAsync(200)
+    await sleepAsync(200.milliseconds)
     inc(completedFutures)
 
   proc vlient3() {.async.} =
-    await sleepAsync(300)
+    await sleepAsync(300.milliseconds)
     inc(completedFutures)
 
   proc vlient4() {.async.} =
-    await sleepAsync(400)
+    await sleepAsync(400.milliseconds)
     inc(completedFutures)
 
   proc vlient5() {.async.} =
-    await sleepAsync(500)
+    await sleepAsync(500.milliseconds)
     inc(completedFutures)
 
   proc vlient1f() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc vlient2f() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc vlient3f() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc vlient4f() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc vlient5f() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client1(): Future[int] {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     result = 1
 
   proc client2(): Future[int] {.async.} =
-    await sleepAsync(200)
+    await sleepAsync(200.milliseconds)
     inc(completedFutures)
     result = 1
 
   proc client3(): Future[int] {.async.} =
-    await sleepAsync(300)
+    await sleepAsync(300.milliseconds)
     inc(completedFutures)
     result = 1
 
   proc client4(): Future[int] {.async.} =
-    await sleepAsync(400)
+    await sleepAsync(400.milliseconds)
     inc(completedFutures)
     result = 1
 
   proc client5(): Future[int] {.async.} =
-    await sleepAsync(500)
+    await sleepAsync(500.milliseconds)
     inc(completedFutures)
     result = 1
 
   proc client1f(): Future[int] {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client2f(): Future[int] {.async.} =
-    await sleepAsync(200)
+    await sleepAsync(200.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client3f(): Future[int] {.async.} =
-    await sleepAsync(300)
+    await sleepAsync(300.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client4f(): Future[int] {.async.} =
-    await sleepAsync(400)
+    await sleepAsync(400.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client5f(): Future[int] {.async.} =
-    await sleepAsync(500)
+    await sleepAsync(500.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
@@ -284,106 +289,106 @@ proc testAllSeq(): int =
   var nfutures = newSeq[Future[int]]()
 
   proc vlient1() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
 
   proc vlient2() {.async.} =
-    await sleepAsync(200)
+    await sleepAsync(200.milliseconds)
     inc(completedFutures)
 
   proc vlient3() {.async.} =
-    await sleepAsync(300)
+    await sleepAsync(300.milliseconds)
     inc(completedFutures)
 
   proc vlient4() {.async.} =
-    await sleepAsync(400)
+    await sleepAsync(400.milliseconds)
     inc(completedFutures)
 
   proc vlient5() {.async.} =
-    await sleepAsync(500)
+    await sleepAsync(500.milliseconds)
     inc(completedFutures)
 
   proc vlient1f() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc vlient2f() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc vlient3f() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc vlient4f() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc vlient5f() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client1(): Future[int] {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     result = 1
 
   proc client2(): Future[int] {.async.} =
-    await sleepAsync(200)
+    await sleepAsync(200.milliseconds)
     inc(completedFutures)
     result = 1
 
   proc client3(): Future[int] {.async.} =
-    await sleepAsync(300)
+    await sleepAsync(300.milliseconds)
     inc(completedFutures)
     result = 1
 
   proc client4(): Future[int] {.async.} =
-    await sleepAsync(400)
+    await sleepAsync(400.milliseconds)
     inc(completedFutures)
     result = 1
 
   proc client5(): Future[int] {.async.} =
-    await sleepAsync(500)
+    await sleepAsync(500.milliseconds)
     inc(completedFutures)
     result = 1
 
   proc client1f(): Future[int] {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client2f(): Future[int] {.async.} =
-    await sleepAsync(200)
+    await sleepAsync(200.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client3f(): Future[int] {.async.} =
-    await sleepAsync(300)
+    await sleepAsync(300.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client4f(): Future[int] {.async.} =
-    await sleepAsync(400)
+    await sleepAsync(400.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client5f(): Future[int] {.async.} =
-    await sleepAsync(500)
+    await sleepAsync(500.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
@@ -464,51 +469,51 @@ proc testAsyncDiscard(): int =
   var completedFutures = 0
 
   proc client1() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
 
   proc client2() {.async.} =
-    await sleepAsync(200)
+    await sleepAsync(200.milliseconds)
     inc(completedFutures)
 
   proc client3() {.async.} =
-    await sleepAsync(300)
+    await sleepAsync(300.milliseconds)
     inc(completedFutures)
 
   proc client4() {.async.} =
-    await sleepAsync(400)
+    await sleepAsync(400.milliseconds)
     inc(completedFutures)
 
   proc client5() {.async.} =
-    await sleepAsync(500)
+    await sleepAsync(500.milliseconds)
     inc(completedFutures)
 
   proc client1f() {.async.} =
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client2f() {.async.} =
-    await sleepAsync(200)
+    await sleepAsync(200.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client3f() {.async.} =
-    await sleepAsync(300)
+    await sleepAsync(300.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client4f() {.async.} =
-    await sleepAsync(400)
+    await sleepAsync(400.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
 
   proc client5f() {.async.} =
-    await sleepAsync(500)
+    await sleepAsync(500.milliseconds)
     inc(completedFutures)
     if true:
       raise newException(ValueError, "")
@@ -524,7 +529,7 @@ proc testAsyncDiscard(): int =
   asyncDiscard client5()
   asyncDiscard client5f()
 
-  waitFor(sleepAsync(2000))
+  waitFor(sleepAsync(2000.milliseconds))
   result = completedFutures
 
 proc testAllZero(): bool =
diff --git a/tests/testsignal.nim b/tests/testsignal.nim
index 05b912af..9a2f4b8e 100644
--- a/tests/testsignal.nim
+++ b/tests/testsignal.nim
@@ -20,7 +20,7 @@ when not defined(windows):
     removeSignal(int(cdata.fd))
 
   proc asyncProc() {.async.} =
-    await sleepAsync(500)
+    await sleepAsync(500.milliseconds)
 
   proc test(signal, value: int): bool =
     discard addSignal(signal, signalProc, cast[pointer](value))
diff --git a/tests/testsoon.nim b/tests/testsoon.nim
index 488ae3f3..0842a91f 100644
--- a/tests/testsoon.nim
+++ b/tests/testsoon.nim
@@ -41,7 +41,7 @@ proc test1(): uint =
 
 proc testProc() {.async.} =
   for i in 1..CallSoonTests:
-    await sleepAsync(100)
+    await sleepAsync(100.milliseconds)
     timeoutsTest1 += 1
 
 proc callbackProc(udata: pointer) {.gcsafe.} =
diff --git a/tests/testtime.nim b/tests/testtime.nim
index a5b1d1fe..b4b6d259 100644
--- a/tests/testtime.nim
+++ b/tests/testtime.nim
@@ -6,16 +6,16 @@
 #  Apache License, version 2.0, (LICENSE-APACHEv2)
 #              MIT license (LICENSE-MIT)
 
-import unittest
+import os, unittest
 import ../chronos, ../chronos/timer
 
 const TimersCount = 10
 
-proc timeWorker(time: int): Future[int] {.async.} =
-  var st = fastEpochTime()
+proc timeWorker(time: Duration): Future[Duration] {.async.} =
+  var st = Moment.now()
   await sleepAsync(time)
-  var et = fastEpochTime()
-  result = int(et - st)
+  var et = Moment.now()
+  result = et - st
 
 proc waitAll[T](futs: seq[Future[T]]): Future[void] =
   var counter = len(futs)
@@ -28,25 +28,34 @@ proc waitAll[T](futs: seq[Future[T]]): Future[void] =
     fut.addCallback(cb)
   return retFuture
 
-proc test(timeout: int): Future[int64] {.async.} =
-  var workers = newSeq[Future[int]](TimersCount)
+proc test(timeout: Duration): Future[Duration] {.async.} =
+  var workers = newSeq[Future[Duration]](TimersCount)
   for i in 0..<TimersCount:
     workers[i] = timeWorker(timeout)
   await waitAll(workers)
-  var sum = 0'i64
+  var sum: Duration
   for i in 0..<TimersCount:
     var time = workers[i].read()
     sum = sum + time
   result = sum div 10'i64
 
+proc testTimer(): bool =
+  let a = Moment.now()
+  waitFor(sleepAsync(1000.milliseconds))
+  let b = Moment.now()
+  let d = b - a
+  result = (d >= 1000.milliseconds) and (d <= 2_000.milliseconds)
+
 when isMainModule:
   suite "Asynchronous timers test suite":
+    test "Timer reliability test [" & asyncTimer & "]":
+      check testTimer() == true
     test $TimersCount & " timers with 10ms timeout":
-      var res = waitFor(test(10))
-      check (res >= 10) and (res <= 100)
+      var res = waitFor(test(10.milliseconds))
+      check (res >= 10.milliseconds) and (res <= 100.milliseconds)
     test $TimersCount & " timers with 100ms timeout":
-      var res = waitFor(test(100))
-      check (res >= 100) and (res <= 1000)
+      var res = waitFor(test(100.milliseconds))
+      check (res >= 100.milliseconds) and (res <= 1000.milliseconds)
     test $TimersCount & " timers with 1000ms timeout":
-      var res = waitFor(test(1000))
-      check (res >= 1000) and (res <= 5000)
+      var res = waitFor(test(1000.milliseconds))
+      check (res >= 1000.milliseconds) and (res <= 5000.milliseconds)