RFC 2616 date/time stamps

Current date:

Mon, 23 Jan 2017 08:34:37 GMT

30 days from now:

Wed, 22 Feb 2017 08:34:37 GMT

365 days from now:

Tue, 23 Jan 2018 08:34:37 GMT

These are they dates you want to use in HTTP headers, such as Last-Modified and Expire, on the Internet.