Merge pull request #22799 from nullaus/bug1049790

bug 1049790 - Use one event listener for system time changes. r=fcampo
(cherry picked from commit 408e24a54fb13217428fa9387ca01044a1ea3da4)

Conflicts:
	shared/js/tz_select.js
Merge pull request #22901 from nullaus/v1.4

Merge pull request #22799 from nullaus/bug1049790