The Evening: Divided Into Two, Commencing at 3 O'Clock, and Sunset
Source: TTT
Exodus 12:6
You must keep it until the fourteenth day of the month, when the whole assembly of the congregation of Israel will slaughter the animals at twilight.
Numbers 9:3
You are to observe it at the appointed time, at twilight on the fourteenth day of this month, in accordance with its statutes and ordinances.”