witching hour

Short definition from Wiktionary

Noun

1. 1
   Often preceded by the: midnight, when witches and other supernatural beings were thought to be active, and to which bad luck was ascribed; also (generally), the middle of the night, when unfortunate things are thought more likely to occur; the dead of night.
2. 2
   A time of day, usually in the early evening, when babies and young children are more fretful and likely to cry or fuss.
3. 3
   The final hour of trading each month during which certain stock options expire, leading to a higher trading volume and greater price volatility.
4. 4
   The hour between 3:00 and 3:59 a.m., associated with demons.