get_date_from_gmt does not properly convert non-DST dates when DST is in effect and vice versa.

[cfinke]

If it is May 1 where I am and daylight-savings time is in effect, and I schedule a post for December 1 at noon (when DST is not in effect) via XML-RPC using the date_created_gmt parameter, my post will actually be scheduled for December 1 at 1pm. This is due to the fact that get_date_from_gmt uses the current timezone offset to convert the date from GMT to local time rather than the timezone offset specific to the date it is converting.

The root issue I suppose is that get_option('gmt_offset') doesn't know when it's getting the gmt_offset for. Fixing that would probably fix a number of other daylight-savings time related issues in Wordpress.

Tested in Wordpress 2.9.2 and the current Wordpress.com.

There is already a pre_option filter on gmt_offset that automatically adjusts the offset for daylight savings - only thing is it assumes you want to know the offset at the time of execution.

I don't think it would be too difficult to add an argument to wp_timezone_override_offset() that allows you to specify a future time for which to calculate an offset. Let me see if I can cobble something together.

Isn't this a duplicate of #9285?

Idea for new function that allows getting gmt offset for a past/future timestamp, which is then called from get_date_from_gmt()

Replying to nacin:

Isn't this a duplicate of #9285?

Possibly, though they are related to different functions. The issue here is that get_date_from_gmt() assumes that the current timezone offset equals the timezone offset for whatever time-string it is given. The issue with #9825 is that get_gmt_from_date() is doing the same thing in reverse.

I think having a get_gmt_offset() function would help fix both of these, rather than having separate timezone-handling code in both of get_date_from_gmt() and get_gmt_from_date(). The main problem is that currently any use of get_option('gmt_offset') assumes that we're dealing with the present.

Please name the PHP version you are experiencing this with and the os and if it's 32 or 64 bit.

This should be handled by either #9285 or #12610.