Pro tip: add test cases to your CI runs with modified system date.
Worked for a few years at a company with a medium-sized codebase whose tests only worked before 6PM.
(Run the tests later than that, and you wind up with some timeframes that span calendar days and therefore break things. Was the underlying code broken, or the tests, or both? Who knows!!)
Was never allowed to fix and investigate. Or to be specific, we were never given the time to fix it. Management simply didn't see it as a problem.
In my younger days I would have gone all HERO HACKER and fixed it anyway on my own time. But now, I know how that turns out. You waste a bunch of evenings fixing it, and usually introduce some other regressions, and you get zero glory and lots of blame. Best case scenario is no regressions and zero glory.
So, screw it. Old-and-jaded me never lifted a finger. If the company doesn't care, why should I?
But, that is an excellent protip. If you are working on a team that actually values things that work. Time/date dependent code is very tricky to get right, especially when multiple time zones are involved. If your test suite doesn't cover multiple possibilities, your code is nearly guaranteed to be wrong.
It's not even like you have to write brand-new, cleverer tests. Just "brute-force" it, assuming your tests are performant:
before:
some_tests
[time_zone_1, time_zone_2, time_zone_3].each do |tz|
[time_of_day1, time_of_day2, time_of_day3].each do |tod|
some_tests(tz, tod)
end
end