Use consistent timezone in jest

[shendy-a8c]

Describe the bug

Currently we use EST as TZ (ref). EST timezone has daylight saving time. This causes GitHub check to fail when there is daylight saving time change.

For example on Nov 6th, 2022, without any code change, GitHub checks that were green (can be seen from this PR and here's the direct link to the green GH check) that was committed as b33be3a became red (can be seen from this my test PR and here's the direct link to the failed GH check).

I think changing the global environment variable TZ to UTC will solve the problem. Some expected values from several tests need to be updated though.

[shendy-a8c]

Since using a UTC would require a lot of changes to the existing unit tests, I think we can just update the tests that I quickly patched in #5065 to either:

• Be daylight saving aware, or
• Set to use consistent timezone just for those test cases, or
• Generate the timezone string dynamically instead of using a hardcoded string as of currently.