diff --git a/README.md b/README.md
index 588c591..31bd840 100644
--- a/README.md
+++ b/README.md
@@ -95,5 +95,20 @@ const myMeasure = timeline.getEntriesByName('foo-measure')[0];
 // {name: 'foo-measure', startTime: 227851.91, duration: 10.5, entryType: 'measure'}
 ```
 
+#### `timestamp` (bool: optional = false)
+
+Add a `timestamp` (unix epoch) value for each mark based on `Date.now()`.
+
+```js
+const Perf = require('performance-node');
+
+const timeline = new Perf({ timestamp: true });
+
+timeline.mark('foo-start');
+
+const myMeasure = timeline.getEntriesByName('foo-start')[0];
+// {name: 'foo-start', startTime: 1.2, duration: 0, entryType: 'mark', timestamp: 1501189303951}
+```
+
 ## Contributing
 - This project uses [Prettier](https://github.com/prettier/prettier). Please execute `npm run eslint -- --fix` to auto-format the code before submitting pull requests.
diff --git a/src/index.js b/src/index.js
index 2d5c0ff..ffdaf96 100644
--- a/src/index.js
+++ b/src/index.js
@@ -13,23 +13,28 @@ function getOffset(timelineInstance) {
 }
 
 function markData(timelineInstance, obj = {}) {
-  const { data = [] } = timelineInstance;
+  const { data = [], useTimestamp } = timelineInstance;
   const defaultHrtime = process.hrtime();
   // set defaults
   const {
     name,
     startTime = hrMillis(defaultHrtime, getOffset(timelineInstance)),
+    timestamp = Date.now(),
     duration = 0,
     entryType = 'mark'
   } = obj;
 
-  const item = {
+  let item = {
     name,
     startTime,
     duration,
     entryType
   };
 
+  if (useTimestamp) {
+    item.timestamp = timestamp;
+  }
+
   return data.concat(item).sort((a, b) => a.startTime - b.startTime);
 }
 
@@ -38,6 +43,7 @@ module.exports = class Timeline {
     this.constructionTimeMillis = hrMillis();
     this.data = [];
     this.offset = kwargs.offset;
+    this.useTimestamp = kwargs.timestamp || false;
     return this;
   }
   mark(name) {
@@ -71,6 +77,7 @@ module.exports = class Timeline {
     this.data = markData(this, {
       name,
       startTime: startMark.startTime,
+      timestamp: startMark.timestamp,
       duration,
       entryType: 'measure'
     });
diff --git a/src/index.test.js b/src/index.test.js
index e571395..5ff43ea 100644
--- a/src/index.test.js
+++ b/src/index.test.js
@@ -47,6 +47,7 @@ test('Can mark one', () => {
   expect(_.isNumber(first.startTime)).toBe(true);
   expect(_.isNumber(first.duration)).toBe(true);
   expect(_.isString(first.name)).toBe(true);
+  expect(first.timestamp).toBe(undefined);
 });
 
 test('Can mark multiple', async () => {
@@ -82,6 +83,7 @@ test('Order of marks is correct', async () => {
   expect(bar1.name).toBe('bar');
   expect(bar2.name).toBe('bar');
   expect(measure.duration).toEqual(bar2.startTime - foo2.startTime);
+  expect(measure.timestamp).toBe(undefined);
 });
 
 test('Can clear marks, measures, and all items', async () => {
@@ -208,6 +210,21 @@ test('The lib uses the custom offset option properly, perf.now should be very si
   expect(_.inRange(number, startMillis - 10, startMillis + 10)).toBe(true);
 });
 
+test('The lib uses the timestamp option properly', async () => {
+  const perf = new lib({ timestamp: true });
+  const before = Date.now() - 1;
+  perf.mark('foo');
+  await delay(10);
+  perf.mark('bar');
+  perf.measure('m1', 'foo', 'bar');
+  const after = Date.now() + 1;
+  const { timestamp } = perf.getEntries()[0];
+  expect(_.isNumber(timestamp)).toBe(true);
+  expect(_.inRange(timestamp, before, after)).toBe(true);
+  const { timestamp: measureTimestamp } = perf.getEntriesByName('m1')[0];
+  expect(measureTimestamp).toBe(timestamp);
+});
+
 test('The code is fast enough', async () => {
   const perf = new lib();