Date Header

Table of Content

  • Syntax
  • Directives
  • Examples
  • Browser Compatibility
  • How to modify Date header The Date header is a standard HTTP header used by the server to indicate the time the response was generated. This header follows a specific HTTP date format, and it's used primarily for caching purposes. The key functionality of the Date header is to allow the client to measure the age of the resource, i.e., the time since it was last fetched from the origin server.


Date: <day-name>, <day> <month> <year> <hour>:<minute>:<second> GMT


  • Day-name: It is the day of the week (Mon, Tue, Wed, ...).
  • Day: It is the day of the month.
  • Month: It's the month of the year (Jan, Feb, Mar, ...).
  • Year: It's the year in 4-digit format.
  • Hour, Minute, Second: It is the time in 24h format, Greenwich Mean Time (GMT).


An example of Date header:

Date: Sun, 06 Nov 1994 08:49:37 GMT

Browser Compatibility

Browser Compatibility
Chrome Supported
Firefox Supported
Safari Supported
Opera Supported
Edge Supported

How to modify Date header

ModHeader is a Google Chrome extension that allows you to modify both the request and response headers of HTTP requests. The way it works is simple. After installing the ModHeader extension from the Chrome webstore, click on its icon and you're greeted with a simple form. You can add the Date in the dropdown of response headers, and set its value to whatever timestamp you want in HTTP date format.

This can be incredibly useful when testing, for example, behavior of your webpage when receiving outdated responses, making ModHeader a powerful tool for web development and testing.