diff --git a/sharness/__snapshots__/example-github-load/data/sourcecred/example-github/timestamps.json b/sharness/__snapshots__/example-github-load/data/sourcecred/example-github/timestamps.json
new file mode 100644
index 0000000..8d01ced
--- /dev/null
+++ b/sharness/__snapshots__/example-github-load/data/sourcecred/example-github/timestamps.json
@@ -0,0 +1 @@
+{"N\u0000sourcecred\u0000git\u0000COMMIT\u00000a223346b4e6dec0127b1e6aa892c4ee0424b66a\u0000":1519807427000,"N\u0000sourcecred\u0000git\u0000COMMIT\u00006bd1b4c0b719c22c688a74863be07a699b7b9b34\u0000":1536806901000,"N\u0000sourcecred\u0000git\u0000COMMIT\u00006d5b3aa31ebb68a06ceb46bbd6cf49b6ccd6f5e6\u0000":1519878354000,"N\u0000sourcecred\u0000git\u0000COMMIT\u0000c430bd74455105f77215ece51945094ceeee6c86\u0000":1536788634000,"N\u0000sourcecred\u0000git\u0000COMMIT\u0000ec91adb718a6045b492303f00d8e8beb957dc780\u0000":1519807271000,"N\u0000sourcecred\u0000git\u0000COMMIT\u0000ecc889dc94cf6da17ae6eab5bb7b7155f577519d\u0000":1519807329000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u000011\u0000420811872\u0000":1536789545000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u000011\u0000420813013\u0000":1536789813000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u000011\u0000420813206\u0000":1536789858000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u000011\u0000420813621\u0000":1536789965000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00002\u0000373768703\u0000":1521217693000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00002\u0000373768850\u0000":1521217725000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00002\u0000385576185\u0000":1525137909000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00002\u0000385576220\u0000":1525137925000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00002\u0000385576248\u0000":1525137939000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00002\u0000385576273\u0000":1525137951000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00002\u0000385576920\u0000":1525138231000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00002\u0000385576936\u0000":1525138238000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00006\u0000373768442\u0000":1521217642000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00006\u0000373768538\u0000":1521217661000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00006\u0000385223316\u0000":1524973307000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000ISSUE\u0000sourcecred\u0000example-github\u00006\u0000417104047\u0000":1535576390000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000PULL\u0000sourcecred\u0000example-github\u00003\u0000369162222\u0000":1519807420000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000PULL\u0000sourcecred\u0000example-github\u00005\u0000396430464\u0000":1528764380000,"N\u0000sourcecred\u0000github\u0000COMMENT\u0000REVIEW\u0000sourcecred\u0000example-github\u00005\u0000100313899\u0000171460198\u0000":1519878210000,"N\u0000sourcecred\u0000github\u0000ISSUE\u0000sourcecred\u0000example-github\u00001\u0000":1519807088000,"N\u0000sourcecred\u0000github\u0000ISSUE\u0000sourcecred\u0000example-github\u000010\u0000":1530297021000,"N\u0000sourcecred\u0000github\u0000ISSUE\u0000sourcecred\u0000example-github\u000011\u0000":1536789479000,"N\u0000sourcecred\u0000github\u0000ISSUE\u0000sourcecred\u0000example-github\u000012\u0000":1536878086000,"N\u0000sourcecred\u0000github\u0000ISSUE\u0000sourcecred\u0000example-github\u000013\u0000":1536878137000,"N\u0000sourcecred\u0000github\u0000ISSUE\u0000sourcecred\u0000example-github\u00002\u0000":1519807129000,"N\u0000sourcecred\u0000github\u0000ISSUE\u0000sourcecred\u0000example-github\u00004\u0000":1519807454000,"N\u0000sourcecred\u0000github\u0000ISSUE\u0000sourcecred\u0000example-github\u00006\u0000":1521217624000,"N\u0000sourcecred\u0000github\u0000ISSUE\u0000sourcecred\u0000example-github\u00007\u0000":1521569949000,"N\u0000sourcecred\u0000github\u0000ISSUE\u0000sourcecred\u0000example-github\u00008\u0000":1521570243000,"N\u0000sourcecred\u0000github\u0000PULL\u0000sourcecred\u0000example-github\u00003\u0000":1519807399000,"N\u0000sourcecred\u0000github\u0000PULL\u0000sourcecred\u0000example-github\u00005\u0000":1519807636000,"N\u0000sourcecred\u0000github\u0000PULL\u0000sourcecred\u0000example-github\u00009\u0000":1525373595000,"N\u0000sourcecred\u0000github\u0000REPO\u0000sourcecred\u0000example-github\u0000":null,"N\u0000sourcecred\u0000github\u0000REVIEW\u0000sourcecred\u0000example-github\u00005\u0000100313899\u0000":1519878210000,"N\u0000sourcecred\u0000github\u0000REVIEW\u0000sourcecred\u0000example-github\u00005\u0000100314038\u0000":1519878296000,"N\u0000sourcecred\u0000github\u0000USERLIKE\u0000BOT\u0000credbot\u0000":null,"N\u0000sourcecred\u0000github\u0000USERLIKE\u0000USER\u0000decentralion\u0000":null,"N\u0000sourcecred\u0000github\u0000USERLIKE\u0000USER\u0000wchargin\u0000":null}
\ No newline at end of file
diff --git a/src/analysis/temporal/timestampMap.js b/src/analysis/temporal/timestampMap.js
new file mode 100644
index 0000000..953f48b
--- /dev/null
+++ b/src/analysis/temporal/timestampMap.js
@@ -0,0 +1,57 @@
+// @flow
+
+import path from "path";
+import fs from "fs-extra";
+import stringify from "json-stable-stringify";
+import * as MapUtil from "../../util/map";
+import {type RepoId, repoIdToString} from "../../core/repoId";
+import {type NodeAddressT, NodeAddress} from "../../core/graph";
+import {type IAnalysisAdapter, type MsSinceEpoch} from "../analysisAdapter";
+import {NodeTrie} from "../../core/trie";
+
+export type TimestampMap = Map<NodeAddressT, MsSinceEpoch | null>;
+
+export function createTimestampMap(
+  nodes: Iterable<NodeAddressT>,
+  adapters: $ReadOnlyArray<IAnalysisAdapter>
+): TimestampMap {
+  const adapterTrie: NodeTrie<IAnalysisAdapter> = new NodeTrie();
+  for (const adapter of adapters) {
+    adapterTrie.add(adapter.declaration().nodePrefix, adapter);
+  }
+  const result = new Map();
+  for (const node of nodes) {
+    const adapter = adapterTrie.getLast(node);
+    if (adapter == null) {
+      throw new Error(`No adapter for ${NodeAddress.toString(node)}`);
+    }
+    result.set(node, adapter.createdAt(node));
+  }
+  return result;
+}
+
+const TIMESTAMP_FILE = "timestamps.json";
+function basepath(sourcecredDirectory: string, repoId: RepoId) {
+  return path.join(sourcecredDirectory, "data", repoIdToString(repoId));
+}
+function filepath(sourcecredDirectory: string, repoId: RepoId) {
+  return path.join(basepath(sourcecredDirectory, repoId), TIMESTAMP_FILE);
+}
+
+export function writeTimestampMap(
+  stamps: TimestampMap,
+  sourcecredDirectory: string,
+  repoId: RepoId
+) {
+  fs.ensureDirSync(basepath(sourcecredDirectory, repoId));
+  const jsonString = stringify(MapUtil.toObject(stamps));
+  fs.writeFileSync(filepath(sourcecredDirectory, repoId), jsonString);
+}
+
+export function readTimestampMap(
+  sourcecredDirectory: string,
+  repoId: RepoId
+): TimestampMap {
+  const contents = fs.readFileSync(filepath(sourcecredDirectory, repoId));
+  return MapUtil.fromObject(JSON.parse(contents.toString()));
+}
diff --git a/src/analysis/temporal/timestampMap.test.js b/src/analysis/temporal/timestampMap.test.js
new file mode 100644
index 0000000..957a4d3
--- /dev/null
+++ b/src/analysis/temporal/timestampMap.test.js
@@ -0,0 +1,87 @@
+// @flow
+
+import tmp from "tmp";
+import {
+  Graph,
+  type NodeAddressT,
+  NodeAddress,
+  EdgeAddress,
+} from "../../core/graph";
+import {makeRepoId} from "../../core/repoId";
+import {
+  createTimestampMap,
+  readTimestampMap,
+  writeTimestampMap,
+} from "./timestampMap";
+
+describe("src/analysis/temporal/timestampMap", () => {
+  const foo = NodeAddress.fromParts(["foo"]);
+  const bar = NodeAddress.fromParts(["bar"]);
+
+  describe("createTimestampMap", () => {
+    const declarationForPrefix = (prefixParts: string[]) => ({
+      name: NodeAddress.fromParts(prefixParts),
+      nodePrefix: NodeAddress.fromParts(prefixParts),
+      edgePrefix: EdgeAddress.fromParts(prefixParts),
+      nodeTypes: [],
+      edgeTypes: [],
+    });
+    const adapterForPrefix = (
+      prefixParts: string[],
+      createdAt: (NodeAddressT) => number | null
+    ) => {
+      class Adapter {
+        declaration() {
+          return declarationForPrefix(prefixParts);
+        }
+        graph() {
+          return new Graph();
+        }
+        createdAt(n: NodeAddressT) {
+          return createdAt(n);
+        }
+      }
+      return new Adapter();
+    };
+    it("matches the most specific adapter", () => {
+      const fooAdapter = adapterForPrefix(["foo"], (_) => 1);
+      const fallbackAdapter = adapterForPrefix([], (_) => null);
+      const nodes = [foo, bar];
+      const tsMap = createTimestampMap(nodes, [fooAdapter, fallbackAdapter]);
+      // foo got its timestamp from the fooAdapter, not from the fallbackAdapter,
+      // even though it matched both.
+      expect(tsMap.get(foo)).toEqual(1);
+      // Bar matched the fallback adapter.
+      expect(tsMap.get(bar)).toEqual(null);
+    });
+    it("throws an error if there is no matching adapter", () => {
+      const foo = NodeAddress.fromParts(["foo"]);
+      expect(() => createTimestampMap([foo], [])).toThrowError(
+        `No adapter for NodeAddress["foo"]`
+      );
+    });
+  });
+  describe("{write,read}TimestampMap", () => {
+    const repo = makeRepoId("foo", "bar");
+    it("throws an error if there is no timestamp map to read", () => {
+      const dir = tmp.dirSync().name;
+      expect(() => readTimestampMap(dir, repo)).toThrowError(
+        "ENOENT: no such file or directory"
+      );
+    });
+    it("can write/read the empty registry", () => {
+      const dir = tmp.dirSync().name;
+      const map = new Map();
+      writeTimestampMap(map, dir, repo);
+      const map2 = readTimestampMap(dir, repo);
+      expect(map2).toEqual(map);
+    });
+    it("can write/read a non-empty registry", () => {
+      const dir = tmp.dirSync().name;
+      const map = new Map([[foo, null], [bar, 3]]);
+      writeTimestampMap(map, dir, repo);
+      const map2 = readTimestampMap(dir, repo);
+      expect(map2).toEqual(map);
+    });
+  });
+});
diff --git a/src/cli/load.js b/src/cli/load.js
index 0cdfc52..6d114ec 100644
--- a/src/cli/load.js
+++ b/src/cli/load.js
@@ -6,15 +6,23 @@ import path from "path";
 
 import * as NullUtil from "../util/null";
 
+import stringify from "json-stable-stringify";
 import * as RepoIdRegistry from "../core/repoIdRegistry";
 import {repoIdToString, stringToRepoId, type RepoId} from "../core/repoId";
 import dedent from "../util/dedent";
 import type {Command} from "./command";
 import * as Common from "./common";
+import {loadGraph, type LoadGraphResult} from "../analysis/loadGraph";
+import {type IBackendAdapterLoader} from "../analysis/analysisAdapter";
+import {
+  createTimestampMap,
+  writeTimestampMap,
+} from "../analysis/temporal/timestampMap";
 
 import execDependencyGraph from "../tools/execDependencyGraph";
 import {loadGithubData} from "../plugins/github/loadGithubData";
 import {loadGitData} from "../plugins/git/loadGitData";
+import {defaultAdapterLoaders} from "./pagerank";
 
 function usage(print: (string) => void): void {
   print(
@@ -193,6 +201,7 @@ export const loadDefaultPlugins = async (options: LoadOptions) => {
     throw new Error("Load tasks failed.");
   }
   addToRepoIdRegistry(options.output);
+  saveTimestamps(defaultAdapterLoaders(), options.output);
   // HACK: Logically, we should have the PagerankTask be included in the
   // first execDependencyGraph run, depending on the other tasks completing.
   //
@@ -261,6 +270,28 @@ function addToRepoIdRegistry(repoId) {
   RepoIdRegistry.writeRegistry(newRegistry, Common.sourcecredDirectory());
 }
 
+async function saveTimestamps(
+  adapterLoaders: $ReadOnlyArray<IBackendAdapterLoader>,
+  repoId: RepoId
+) {
+  const loadGraphResult: LoadGraphResult = await loadGraph(
+    Common.sourcecredDirectory(),
+    adapterLoaders,
+    repoId
+  );
+  if (loadGraphResult.status !== "SUCCESS") {
+    throw new Error(`Unable to load graph: ${stringify(loadGraphResult)}`);
+  }
+  const {graph} = loadGraphResult;
+  // We load all the adapters twice (once in loadGraph, once here).
+  // Could de-duplicate, but it's marginal overhead compared to loading the data.
+  const adapters = await Promise.all(
+    adapterLoaders.map((a) => a.load(Common.sourcecredDirectory(), repoId))
+  );
+  const timestampMap = createTimestampMap(graph.nodes(), adapters);
+  writeTimestampMap(timestampMap, Common.sourcecredDirectory(), repoId);
+}
+
 export const help: Command = async (args, std) => {
   if (args.length === 0) {
     usage(std.out);
diff --git a/src/cli/pagerank.js b/src/cli/pagerank.js
index 64ecfd0..c64dfc2 100644
--- a/src/cli/pagerank.js
+++ b/src/cli/pagerank.js
@@ -169,6 +169,8 @@ export async function savePagerankGraph(
   await fs.writeFile(pgFile, stringify(pgJSON));
 }
 
+// TODO(#1120): This should be canonicalized somewhere more appropriate,
+// e.g. in src/plugins/defaultPlugins.js
 export const defaultAdapterLoaders = () => [
   new GithubAdapterLoader(),
   new GitAdapterLoader(),