RFC 2616 date/time stamps

Current date:

Sun, 19 Nov 2017 19:40:34 GMT

30 days from now:

Tue, 19 Dec 2017 19:40:34 GMT

365 days from now:

Mon, 19 Nov 2018 19:40:34 GMT

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