merged branch mlehner/default_timezone (PR #635)

merged branch mlehner/default_timezone (PR #635)

Commits
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5699753 added setTimezone to allow globally overriding the timezone when formating dates

Discussion
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Allow setting global timezone for date formatting

My API returns dates in a string format of 2012-02-14T00:35:37+00:00. When parsed by the DateTime constructor, the timezone for that new object is UTC. Without specifying every time I use the date filter there was no way to globally influence the timezone used.

I added setTimezone() to the core extension that functions similar to setDateFormat() except that there is no timezone set by default to allow for backwards compatibility.