BUG: Time/date calculation not based on UTC

[Stephanus]

The time calculation for "when has smth been posted" is based on the timezone and not on a correct UTC difference calculations.

E.g.: User A) has time zone PST set in the settings and posts at 8:00h GMT+1 (which is his browser and OS setting) and User B) has also PST set in settings, but the browser is using the correct GMT+1.

Then the post is displayed as "yesterday". 

The moment User B) switches to GMT+1 then it is correctly calculated.

This shows that the calculation is based on the absolute time with timezone and not on UTC timing. 

The attached picture with "yesterday" was taken before the one with "5 hours".

P.S.: during creation of the profile the timezone should be set correctly AND the available timezones are confusing as these do not represent the default timezones of other systems, e.g. Windows.