RFC 2616 date/time stamps

Current date:

Fri, 26 May 2017 18:54:07 GMT

30 days from now:

Sun, 25 Jun 2017 18:54:07 GMT

365 days from now:

Sat, 26 May 2018 18:54:07 GMT

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