The Jewish day begins and ends at sundown. Which means, say the commentaries, that the day moves through darkness to light.
The consequence is that Jewish holidays begin on the evening of the first day and end at sundown on the last day.
‘Erev’ Pesach is the first evening of Passover, and this year it is on the 2nd April (14 Nisan 5767 in the Hebrew Calendar), and maybe I can be the first to send a card : )
Card design © David Bennett