diff --git a/scm/Mercurial.cpp b/scm/Mercurial.cpp
index a0b76cb5637a..b911b5336198 100644
--- a/scm/Mercurial.cpp
+++ b/scm/Mercurial.cpp
@@ -1,6 +1,9 @@
 /* Copyright 2017-present Facebook, Inc.
  * Licensed under the Apache License, Version 2.0 */
 #include "Mercurial.h"
+#include <chrono>
+#include <cmath>
+#include <cstdio>
 #include "ChildProcess.h"
 #include "Logging.h"
 #include "watchman.h"
@@ -8,6 +11,8 @@
 // Capability indicating support for the mercurial SCM
 W_CAP_REG("scm-hg")
 
+using namespace std::chrono;
+
 namespace watchman {
 
 std::string hgExecutablePath() {
@@ -260,4 +265,32 @@ SCM::StatusResult Mercurial::getFilesChangedBetweenCommits(
   return result;
 }
 
+time_point<system_clock> Mercurial::getCommitDate(
+    w_string_piece commitId,
+    w_string requestId) const {
+  ChildProcess proc(
+      {hgExecutablePath(), "log", "-r", commitId.data(), "-T", "{date}\n"},
+      makeHgOptions(requestId));
+  auto outputs = proc.communicate();
+  auto status = proc.wait();
+  if (status) {
+    throw std::runtime_error(to<std::string>(
+        "failed query for hg log; command returned with status ",
+        status,
+        " out=",
+        outputs.first,
+        " err=",
+        outputs.second));
+  }
+  return Mercurial::convertCommitDate(outputs.first.c_str());
+}
+
+time_point<system_clock> Mercurial::convertCommitDate(const char* commitDate) {
+  double date;
+  if (std::sscanf(commitDate, "%lf", &date) != 1) {
+    throw std::runtime_error(to<std::string>(
+        "failed to parse date value `", commitDate, "` into a double"));
+  }
+  return system_clock::from_time_t(date);
+}
 } // namespace watchman
diff --git a/scm/Mercurial.h b/scm/Mercurial.h
index ee3afe4d2e90..7b228da1d997 100644
--- a/scm/Mercurial.h
+++ b/scm/Mercurial.h
@@ -24,6 +24,12 @@ class Mercurial : public SCM {
       w_string_piece commitA,
       w_string_piece commitB,
       w_string requestId = nullptr) const override;
+  std::chrono::time_point<std::chrono::system_clock> getCommitDate(
+      w_string_piece commitId,
+      w_string requestId = nullptr) const override;
+  // public for testing
+  static std::chrono::time_point<std::chrono::system_clock> convertCommitDate(
+      const char* commitDate);
 
  private:
   // Returns options for invoking hg
diff --git a/scm/SCM.h b/scm/SCM.h
index 8b387dfb2691..1b7b83a4bd29 100644
--- a/scm/SCM.h
+++ b/scm/SCM.h
@@ -2,6 +2,7 @@
  * Licensed under the Apache License, Version 2.0 */
 #pragma once
 #include "watchman_system.h"
+#include <chrono>
 #include <memory>
 #include <vector>
 #include "watchman_string.h"
@@ -62,6 +63,12 @@ class SCM {
       w_string_piece commitB,
       w_string requestId = nullptr) const = 0;
 
+  // Compute the source control date associated with the specified
+  // commit.
+  virtual std::chrono::time_point<std::chrono::system_clock> getCommitDate(
+      w_string_piece commitId,
+      w_string requestId = nullptr) const = 0;
+
  private:
   w_string rootPath_;
   w_string scmRoot_;
diff --git a/tests/MercurialTest.cpp b/tests/MercurialTest.cpp
new file mode 100644
index 000000000000..3c0bb32c4a2e
--- /dev/null
+++ b/tests/MercurialTest.cpp
@@ -0,0 +1,22 @@
+/* Copyright 2016-present Facebook, Inc.
+ * Licensed under the Apache License, Version 2.0. */
+
+#include "scm/Mercurial.h"
+#include "thirdparty/tap.h"
+#include "watchman.h"
+
+using namespace std::chrono;
+
+void test_convert_date() {
+  auto date = watchman::Mercurial::convertCommitDate("1529420960.025200");
+  auto result = duration_cast<seconds>(date.time_since_epoch()).count();
+  auto expected = 1529420960;
+  ok(result == expected, "Expected %d but observed %d", expected, result);
+}
+
+int main(int, char**) {
+  plan_tests(1);
+  test_convert_date();
+
+  return exit_status();
+}
diff --git a/tests/TARGETS b/tests/TARGETS
index 8f783ecdfb64..e23df5d55007 100644
--- a/tests/TARGETS
+++ b/tests/TARGETS
@@ -202,3 +202,13 @@ t_test(
         "//watchman:testsupport",
     ],
 )
+
+t_test(
+    name = "mercurialTest",
+    srcs = [
+        "MercurialTest.cpp",
+    ],
+    deps = [
+        "//watchman:watchmanlib",
+    ],
+)
diff --git a/watcher/eden.cpp b/watcher/eden.cpp
index 45f401a4ec93..20cd988891b6 100644
--- a/watcher/eden.cpp
+++ b/watcher/eden.cpp
@@ -561,6 +561,12 @@ class EdenWrappedSCM : public SCM {
     return inner_->getFilesChangedBetweenCommits(commitA, commitB);
   }
 
+  std::chrono::time_point<std::chrono::system_clock> getCommitDate(
+      w_string_piece commitId,
+      w_string requestId = nullptr) const override {
+    return inner_->getCommitDate(commitId, requestId);
+  }
+
   static std::unique_ptr<EdenWrappedSCM> wrap(std::unique_ptr<SCM> inner) {
     if (!inner) {
       return nullptr;