the same night; that night
Used in news reports and formal contexts to refer to a night previously mentioned. Often adverbial, meaning 'on the same night' or 'that night'.
That same night, another incident occurred in the city.
The press conference was held that night.
That night, a fire broke out in a nearby warehouse.
At around 11 p.m. that night, a suspicious person was seen near the scene.
当夜 means 'the night in question' and looks similar to 同夜, but 当夜 emphasizes the night of a specific event rather than referring back to a previously mentioned night.
Compound of 同 (どう, 'same') and 夜 (や, 'night').