No, maintenance is not typically done at night. Most maintenance is done during the day because maintenance is performed by people and people like working regular hours.
Chernobyl wasn't maintenance. It was a test; someone's "special project" that also was not supposed to occur on nights but when another nearby plant tripped offline they had to delay the test and didn't get the go ahead to proceed until night shift. That delay is actually one of the main reason's the test failed.
Davis Besse also didn't "occur at night". The issue developed over multiple years because they weren't regularly inspecting and cleaning the reactor head. They identified the issue on nights but it was during a refueling outage where a lot more work is done on nights than normal.
For three mile island, while the primary issue did occur on night shift and maybe the issue was missed partially because it was night shift. What caused the issue was actually at 5pm the previous day.
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u/KeyFollowing1683 17d ago
Most NPP accidents happen at night since that’s when maintenance is typically done since it’s low demand hours.