[RFC|Merged] Switch to PHP timezone handling

[AmigoJack]

It's not that we need to actually pre-select the right time zone - the whole list could be filtered, so only time zones show up which are +/- 2 or 3 hours of the current local time. Because there is no rule that daylight saving is always 1 hour delta.

[nickvergessen]

Oleg can you rebase this on develop, there are some strange conflicts in install/database_update.php with your last commit.

[Oleg]

I got as far as plurals for now.

[nickvergessen]

I updated the branch of oleg to develop and worked a bit on it:
https://github.com/nickvergessen/phpbb3 ... z-handling

The selection is now made in 2 steps:
1. Select your current time (limits the number of timezones in step 2)
2. Select the actual timezone

Without Javascript, we can not do much, but give the hole list:

[naderman]

Sounds good.

[Oleg]

I like, I think.

[naderman]

Please make sure, the feature PR includes a functional test.

[nickvergessen]

Todo:

• Change selection in ACP
• Change selection in subsilver2
• Add function to calculate the unix timestamp of a given user date and time
• Add code to update
• Write tests

[Oleg]

From what I recall language had to be changed to use 3.1 plurals and migrations/install code needed to be written.

[nickvergessen]

I would not know, where plurals are used, but I will review it. thanks for rementioning.