datetime: Make use of new g_time_zone_new_identifier() that properly handles errors

g_time_zone_new() returns UTC if it fails to parse the timezone
identifier, which is rather suboptimal and causes wrong datetimes to be
created silently.
35 jobs for !706 with datetime-cleanup in 51 seconds (queued for 5 seconds)
detached
Status Job ID Name Coverage
  Build Docker
passed #5799498
alpine amd64 manifest builder docker

00:00:35

passed #5799497
android docker

00:00:31

passed #5799495
cerbero fedora amd64 docker

00:00:28

passed #5799493
fedora amd64 docker

00:00:34

passed #5799500
gst-indent amd64 docker

00:00:30

 
  Preparation
passed #5799503
gst indent

00:00:15

manual #5799502
manual
manifest
 
  Build
created #5799520
gstreamer
build cerbero cross-android universal
created #5799528
gst-ios-13.2
build cerbero cross-ios universal
created #5799522
gstreamer
build cerbero cross win32
created #5799524
gstreamer
build cerbero cross win64
created #5799518
gstreamer
build cerbero fedora x86_64
created #5799526
gst-macos-10.15
build cerbero macos x86_64
created #5799530
1809 gstreamer-windows windows docker
build cerbero msvc x86_64
created #5799510
build clang fedora x86_64
created #5799516
1809 windows docker allowed to fail manual
build msys2
created #5799505
build nodebug fedora x86_64
created #5799507
build static fedora x86_64
created #5799508
build static nodebug fedora x86_64
created #5799511
1809 windows docker
build vs2017 amd64
created #5799514
1809 windows docker
build vs2017 x86
 
  Test
created #5799533
gstreamer
check fedora
created #5799535
gstreamer
integration testsuites fedora 1/4
created #5799536
gstreamer
integration testsuites fedora 2/4
created #5799537
gstreamer
integration testsuites fedora 3/4
created #5799538
gstreamer
integration testsuites fedora 4/4
created #5799543
gstreamer
valgrind bad
created #5799540
gstreamer
valgrind base
created #5799539
gstreamer
valgrind core
created #5799544
gstreamer
valgrind ges
created #5799541
gstreamer
valgrind good
created #5799542
gstreamer
valgrind ugly
 
  Integrate
created #5799545
cross-android universal examples
created #5799547
gst-ios-13.2
cross-ios universal examples
created #5799546
documentation