I once only had a test that failed Saturday evenings. We didn't notice it for the longest time because generally, people don't check in code then, because they'

I once only had a test that failed Saturday evenings. We didn't notice it for the longest time because generally, people don't check in code then, because they're not working. The test dealt with a "week", and on Saturday evening, the current week in UTC differed from that of the local timezone.