strtotime("thursday, november ".date("Y")." + 3 weeks")
That gives me Thanksgiving. Awesome. It is cool for other stuff too. At its very basic, it can take a MySQL datetime field and turn it into a timestamp. Very handy for date calculations. It also understands RFC 2822 and ISO 8601 date formats. These are common in HTTP headers and some XML documents like RSS and Atom feeds. Also, PHP can output those two standard formats with the date() function. So, this makes them a good standards compliant way to pass full, timezone specific dates around.