diff --git a/pkgs/clock/lib/clock.dart b/pkgs/clock/lib/clock.dart
new file mode 100644
index 0000000..4285587
--- /dev/null
+++ b/pkgs/clock/lib/clock.dart
@@ -0,0 +1,151 @@
+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+part of quiver.time;
+
+/// Provides current time
+abstract class TimeProvider {
+  DateTime call();
+}
+
+class _SystemTimeProvider implements TimeProvider {
+  const _SystemTimeProvider();
+  DateTime call() => new DateTime.now();
+}
+
+/// Same as [TimeProvider] but in the form of a function.
+typedef DateTime TimeFunction();
+
+/// Time provider that gets time from a function.
+class FunctionTimeProvider implements TimeProvider {
+  final TimeFunction _timeFunction;
+  FunctionTimeProvider(DateTime this._timeFunction());
+  DateTime call() => _timeFunction();
+}
+
+/// Always returns time provided by user. Useful in unit-tests.
+class FixedTimeProvider implements TimeProvider {
+  DateTime time;
+  FixedTimeProvider(this.time);
+  DateTime call() => time;
+}
+
+/// Uses system clock to obtain current time
+const TimeProvider SYSTEM_TIME = const _SystemTimeProvider();
+
+/// Provides points in time relative to the current point in time. The current
+/// point in time is defined by a [TimeProvider] (see constructors for how to
+/// supply time providers).
+class Clock {
+
+  final TimeProvider _time;
+
+  /// Creates [Clock] based on the system clock.
+  Clock() : _time = SYSTEM_TIME;
+
+  /// Creates [Clock] based on user-defined [TypeProvider].
+  Clock.custom(this._time);
+
+  /// Creates [Clock] that uses the time provided by the user as the current
+  /// time.
+  Clock.fixed(DateTime time) : _time = new FixedTimeProvider(time);
+
+  /// Create [Clock] that gets time from a function.
+  Clock.fromFunc(TimeFunction func) : _time = new FunctionTimeProvider(func);
+
+  /// Returns current time.
+  DateTime now() => _time();
+
+  /// Returns the point in time [Duration] amount of time ago.
+  DateTime ago(Duration duration) => now().subtract(duration);
+
+  /// Returns the point in time [Duration] amount of time from now.
+  DateTime fromNow(Duration duration) => now().add(duration);
+
+  /// Return the point in time [micros] microseconds ago.
+  DateTime microsAgo(int micros) => ago(new Duration(microseconds: micros));
+
+  /// Return the point in time [micros] microseconds from now.
+  DateTime microsFromNow(int micros) => microsAgo(-micros);
+
+  /// Return the point in time [millis] milliseconds ago.
+  DateTime millisAgo(int millis) => ago(new Duration(milliseconds: millis));
+
+  /// Return the point in time [millis] milliseconds from now.
+  DateTime millisFromNow(int millis) => millisAgo(-millis);
+
+  /// Return the point in time [seconds] ago.
+  DateTime secondsAgo(int seconds) => ago(new Duration(seconds: seconds));
+
+  /// Return the point in time [seconds] from now.
+  DateTime secondsFromNow(int seconds) => secondsAgo(-seconds);
+
+  /// Return the point in time [minutes] ago.
+  DateTime minutesAgo(int minutes) => ago(new Duration(minutes: minutes));
+
+  /// Return the point in time [minutes] from now.
+  DateTime minutesFromNow(int minutes) => minutesAgo(-minutes);
+
+  /// Return the point in time [hours] ago.
+  DateTime hoursAgo(int hours) => ago(new Duration(hours: hours));
+
+  /// Return the point in time [hours] from now.
+  DateTime hoursFromNow(int hours) => hoursAgo(-hours);
+
+  /// Return the point in time [days] ago.
+  DateTime daysAgo(int days) => ago(new Duration(days: days));
+
+  /// Return the point in time [days] from now.
+  DateTime daysFromNow(int days) => daysAgo(-days);
+
+  /// Return the point in time [weeks] ago.
+  DateTime weeksAgo(int weeks) => ago(new Duration(days: 7 * weeks));
+
+  /// Return the point in time [weeks] from now.
+  DateTime weeksFromNow(int weeks) => weeksAgo(-weeks);
+
+  /// Return the point in time [months] ago on the same date.
+  DateTime monthsAgo(int months) {
+    var time = now();
+    return new DateTime(
+        time.year,
+        time.month - months,
+        time.day,
+        time.hour,
+        time.minute,
+        time.second,
+        time.millisecond
+    );
+  }
+
+  /// Return the point in time [months] from now on the same date.
+  DateTime monthsFromNow(int months) => monthsAgo(-months);
+
+  /// Return the point in time [years] ago on the same date.
+  DateTime yearsAgo(int years) {
+    var time = now();
+    return new DateTime(
+        time.year - years,
+        time.month,
+        time.day,
+        time.hour,
+        time.minute,
+        time.second,
+        time.millisecond
+    );
+  }
+
+  /// Return the point in time [years] from now on the same date.
+  DateTime yearsFromNow(int years) => yearsAgo(-years);
+}
diff --git a/pkgs/clock/test/clock_test.dart b/pkgs/clock/test/clock_test.dart
new file mode 100644
index 0000000..614a9e9
--- /dev/null
+++ b/pkgs/clock/test/clock_test.dart
@@ -0,0 +1,175 @@
+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+library quiver.iterables.merge_test;
+
+import 'package:unittest/unittest.dart';
+import 'package:quiver/time.dart';
+
+main() {
+  group('clock', () {
+    var subject = new Clock.fixed(new DateTime(2013));
+
+    test("should return time based on system time and not fail", () {
+      expect(new Clock(), isNotNull);
+    });
+
+    test("should return time provided by custom TimeProvider", () {
+      var fixedTimeProvider = new FixedTimeProvider(new DateTime(2013));
+      var fixedClock = new Clock.custom(fixedTimeProvider);
+      expect(fixedClock.now(), new DateTime(2013));
+
+      fixedTimeProvider.time = new DateTime(2014);
+      expect(fixedClock.now(), new DateTime(2014));
+    });
+
+    test("should return fixed time", () {
+      expect(new Clock.fixed(new DateTime(2013)).now(), new DateTime(2013));
+    });
+
+    test("should return time provided by custom TimeFunction", () {
+      expect(new Clock.fromFunc(() => new DateTime(2013)).now(),
+          new DateTime(2013));
+    });
+
+    test("should return time Duration ago", () {
+      expect(subject.ago(new Duration(days: 366)), new DateTime(2012));
+    });
+
+    test("should return time Duration from now", () {
+      expect(subject.fromNow(new Duration(days: 365)), new DateTime(2014));
+    });
+
+    test("should return time micros ago", () {
+      expect(subject.microsAgo(1000),
+          new DateTime(2012, 12, 31, 23, 59, 59, 999));
+    });
+
+    test("should return time micros from now", () {
+      expect(subject.microsFromNow(1000),
+          new DateTime(2013, 1, 1, 0, 0, 0, 1));
+    });
+
+    test("should return time millis ago", () {
+      expect(subject.millisAgo(1000),
+          new DateTime(2012, 12, 31, 23, 59, 59, 000));
+    });
+
+    test("should return time millis from now", () {
+      expect(subject.millisFromNow(3),
+          new DateTime(2013, 1, 1, 0, 0, 0, 3));
+    });
+
+    test("should return time seconds ago", () {
+      expect(subject.secondsAgo(10),
+          new DateTime(2012, 12, 31, 23, 59, 50, 000));
+    });
+
+    test("should return time seconds from now", () {
+      expect(subject.secondsFromNow(3),
+          new DateTime(2013, 1, 1, 0, 0, 3, 0));
+    });
+
+    test("should return time minutes ago", () {
+      expect(subject.minutesAgo(10),
+          new DateTime(2012, 12, 31, 23, 50, 0, 000));
+    });
+
+    test("should return time minutes from now", () {
+      expect(subject.minutesFromNow(3),
+          new DateTime(2013, 1, 1, 0, 3, 0, 0));
+    });
+
+    test("should return time hours ago", () {
+      expect(subject.hoursAgo(10),
+          new DateTime(2012, 12, 31, 14, 0, 0, 000));
+    });
+
+    test("should return time hours from now", () {
+      expect(subject.hoursFromNow(3),
+          new DateTime(2013, 1, 1, 3, 0, 0, 0));
+    });
+
+    test("should return time days ago", () {
+      expect(subject.daysAgo(10),
+          new DateTime(2012, 12, 22, 0, 0, 0, 000));
+    });
+
+    test("should return time days from now", () {
+      expect(subject.daysFromNow(3),
+          new DateTime(2013, 1, 4, 0, 0, 0, 0));
+    });
+
+    test("should return time months ago on the same date", () {
+      expect(subject.monthsAgo(1),
+          new DateTime(2012, 12, 1, 0, 0, 0, 000));
+      expect(subject.monthsAgo(2),
+          new DateTime(2012, 11, 1, 0, 0, 0, 000));
+      expect(subject.monthsAgo(3),
+          new DateTime(2012, 10, 1, 0, 0, 0, 000));
+      expect(subject.monthsAgo(4),
+          new DateTime(2012, 9, 1, 0, 0, 0, 000));
+    });
+
+    test("should return time months from now on the same date", () {
+      expect(subject.monthsFromNow(1),
+          new DateTime(2013, 2, 1, 0, 0, 0, 0));
+      expect(subject.monthsFromNow(2),
+          new DateTime(2013, 3, 1, 0, 0, 0, 0));
+      expect(subject.monthsFromNow(3),
+          new DateTime(2013, 4, 1, 0, 0, 0, 0));
+      expect(subject.monthsFromNow(4),
+          new DateTime(2013, 5, 1, 0, 0, 0, 0));
+    });
+
+    test("should return time years ago on the same date", () {
+      expect(subject.yearsAgo(1),
+          new DateTime(2012, 1, 1, 0, 0, 0, 000));  // leap year
+      expect(subject.yearsAgo(2),
+          new DateTime(2011, 1, 1, 0, 0, 0, 000));
+      expect(subject.yearsAgo(3),
+          new DateTime(2010, 1, 1, 0, 0, 0, 000));
+      expect(subject.yearsAgo(4),
+          new DateTime(2009, 1, 1, 0, 0, 0, 000));
+      expect(subject.yearsAgo(5),
+          new DateTime(2008, 1, 1, 0, 0, 0, 000));  // leap year
+      expect(subject.yearsAgo(6),
+          new DateTime(2007, 1, 1, 0, 0, 0, 000));
+      expect(subject.yearsAgo(30),
+          new DateTime(1983, 1, 1, 0, 0, 0, 000));
+      expect(subject.yearsAgo(2013),
+          new DateTime(0, 1, 1, 0, 0, 0, 000));
+    });
+
+    test("should return time years from now on the same date", () {
+      expect(subject.yearsFromNow(1),
+          new DateTime(2014, 1, 1, 0, 0, 0, 0));
+      expect(subject.yearsFromNow(2),
+          new DateTime(2015, 1, 1, 0, 0, 0, 0));
+      expect(subject.yearsFromNow(3),
+          new DateTime(2016, 1, 1, 0, 0, 0, 0));
+      expect(subject.yearsFromNow(4),
+          new DateTime(2017, 1, 1, 0, 0, 0, 0));
+      expect(subject.yearsFromNow(5),
+          new DateTime(2018, 1, 1, 0, 0, 0, 0));
+      expect(subject.yearsFromNow(6),
+          new DateTime(2019, 1, 1, 0, 0, 0, 0));
+      expect(subject.yearsFromNow(30),
+          new DateTime(2043, 1, 1, 0, 0, 0, 0));
+      expect(subject.yearsFromNow(1000),
+          new DateTime(3013, 1, 1, 0, 0, 0, 0));
+    });
+
+  });
+}