http://us3.php.net/migration55 '5 months ago' - no explicit date, nice to have, but please add explicit data so people can talk about the entry from day XY

http://us3.php.net/download-docs.php "d-M-Y"

http://www.php.net/archive/2013.php#id2013-10-10-1 in URL "Y-m-d", in page "d-M-Y"

http://talks.php.net/index.php/PHP+5 "M d, Y" (Total = 4)

(I removed the rest. Bug reporting system said "Please do not SPAM our bug system." Are PHP sources SPAM?)

http://news.php.net/php.announce "D M  j H:i:s Y", the second space before the j only occurs for j<10. The format cannot be expressed with the php formatting codes. (Total = 5)

https://git.php.net/ '18 hours ago' - no explicit date

https://git.php.net/?p=web/gtk.git;a=summary "Y-m-d" + "D, j M Y H:i:s O (H:i O)" , where the second H, i, O differ from the first (Total = 6)

http://news.php.net/group.php?group=php.announce&format=rss "D, d M Y H:i:s O" (Total = 7)

http://pear.php.net/ "D, jS M y" (Total = 8)

http://pear.php.net/package/HTTP_OAuth/ "Y-m-d" (fine)

http://pear.php.net/package/Auth/download/ "Y-m-d H:i" (fine)

http://pear.php.net/bugs/search.php?cmd=display&package_name%5B%5D=Auth "Y-m-d" (fine)

http://pear.php.net/manual/en/about-pear.php "D, j M Y" or "D, d M Y" only two digit example found, so format not clear.

http://pecl.php.net/ "Y-m-d" (fine)

http://pecl.php.net/news/ "Y-m-d" (fine)

http://pecl.php.net/package/stats "Y-m-d" (fine)

http://marc.info/?l=pecl-dev "Y-m-d" (fine)

http://snaps.php.net/ "M j, Y H:i" or "M d, Y H:i" only two digit example found, so format not clear.  (Total = 9)

(It thinks it is spam becomes there are so many links :))

Thanks for the report, you raise an excellent point!

This many date formats in use bothers me as well. I'll look into pruning them a bit.

http://www.python.org/ now uses Y-m-d. 

In Gmail web interface I also see that more of my reply emails write something like: "2014-03-04 2:58 GMT+01:00 Name <name@example.org>:" (Note, they miss the leading 0 for one digit hours and use GMT which is wrong, correct is UTC).

Human readable dates will be displayed as 'd M Y'. Datetimes intended for tools will use RFC 3339 (W3C is the same thing). Dates intended for tools (no timestamp information) will use 'Y-m-d'.

I have committed some changes already and plan to work on this today during stretches where my code is compiling.

"Human readable dates will be displayed as 'd M Y'. Datetimes intended for tools will use RFC 3339 (W3C is the same thing). Dates intended for tools (no timestamp information) will use 'Y-m-d'."

That again is three formats. On a website all displayed date information can be read by humans. Y-m-d is perfectly readable by humans - at least me and probably the designers of https://www.python.org/ thought so. Y-m-d is defined in ISO 8601 and it is the most compact format of those that are not ambiguous. Straight forward. No RFCs with their handful of formats, no W3C (they themselves don't use it strictly on their site), just one ISO.

Y-m-d is already the most used format on php.net when looking at the links provided on creation of this bug.

Just convert the others to Y-m-d and you are done.

> That again is three formats.

Don't be an arse; going from 9 formats to 3 formats is a significant improvement. It's technically only 2 formats as the third is included in the second; I was just being explicit that some things don't have an associated time.

@levim's "Don't be an arse;" 

ISO 8601 was not my invention.
 
Here is another source that references it https://xkcd.com/1179/

> […]; going from 9 formats to 3 formats is a significant
> improvement.

And certainly good enough.