This is to prepare for removing the time zone from DateTime's default
format string. The date utility on most system show time zone by default
so let's keep that.
This reverts most of commit ede5c9548e.
The one change not reverted is ClockWidget.h, so that the taskbar clock
can continue to notice time zone changes.
In most applications, we invoke tzset once at startup for now. Most of
these are short lived and don't need to know about time zone changes.
The exception is the ClockWidget in the taskbar. Here, we invoke tzset
each time we update the system time. This way, any time zone changes can
take effect immediately.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
