How to find out what the date was 5 days ago?

Question

Well, the following returns what date was 5 days ago:

$days_ago = date(\'Y-m-d\', mktime(0, 0, 0, date(\"m\") , date(\"d\") - 5, date(\"Y\")));

Answer 1

General algorithms for date manipulation convert dates to and from Julian Day Numbers. Here is a link to a description of such algorithms, a description of the best algorithms currently known, and the mathematical proofs of each of them: http://web.archive.org/web/20140910060704/http://mysite.verizon.net/aesir_research/date/date0.htm