RFC 2616 date/time stamps

Current date:

Sun, 04 Dec 2016 01:50:14 GMT

30 days from now:

Tue, 03 Jan 2017 01:50:14 GMT

365 days from now:

Mon, 04 Dec 2017 01:50:14 GMT

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