Time Travel

A browser extension to fake the current date and time in JavaScript Date or Intl.DateTimeFormat objects, to help you debug time-dependent frontend applications without having to change the system time.

time-travel-1.3.6.demo.mp4

Usage

• Open the tab you want to change the time in.
• Click the Extensions icon in the toolbar, then click Time Travel.
• Edit the date and time in the input field directly, or click the calendar icon to choose the date visually.
• Confirm with Enter or by clicking the "Change Date" button. In chrome, when first activating the extension on a tab, the page needs to be reloaded once to apply the changes.
• Any JavaScript Date or Intl.DateTimeFormat in the current tab now returns the fake date/time you set.

To restore the system time, click the extension icon and press Reset.

When the fake time is turned on, the clock is paused by default. Press the play (▶) button to make the fake clock tick forward at a normal rate, press stop (⏹) to pause the clock.

Example Dates and Formats

• 2023-04-27 12:40 - Local time
• 2023-04-27 - Midnight UTC
• 2025-03-30 00:59:55 - Assuming your system timezone is Europe/London (GMT), 5 seconds before a one-hour jump to 2 a.m. (summer time)
• 2023-04-27T12:40Z - Set local equivalent for given UTC time
• 2023-04-27T12:40+1130 - Set local equivalent for time with +11:30 timezone offset. Note that actual time zone is not changed
• 2023-03-25T12:40:00.120 - Local time with milliseconds
• 1731493140025 - UNIX timestamp

Features

• Fakes date and time for all methods of Date and Intl.DateTimeFormat objects.
• Time can be stopped and resumed.
• Minimal permissions, only affects current tab after clicking the extension icon. (Only in Chrome)

Limitations

• Only JavaScript is affected by the extension.
• Some functionality or animations may behave strangely if the clock is stopped. Try resuming the clock via the ▶ button in that case.
• The extension does not work in iframes with the sandbox attribute.

Installation

For Chrome, Edge, and other Chromium-based browsers, install the extension from the Chrome Web Store: https://chrome.google.com/webstore/detail/time-travel/jfdbpgcmmenmelcghpbbkldkcfiejcjg

For Firefox, install it from: https://addons.mozilla.org/en-US/firefox/addon/timetravel/

Development

To build and use a local version:

• Clone this repository and run pnpm install.
• Run pnpm dev (or pnpm build for a production version).

Chrome

• Open chrome://extensions and enable 'Developer Mode'.
• Click 'Load unpacked' and select the dist/chrome directory

Firefox

Change into dist/firefox and start npx web-ext run to start a new Firefox instance with the extension loaded.

Or, manually

• Open about:debugging
• Navigate to 'This Firefox'
• Click 'Temporary Extensions' > 'Load Temporary Add-on...' and select dist/firefox/manifest.json.