Preparation for the Passover is instructed in Shemoth (Exodus) 12 and starts on the 10th day of Aviv until the 14th day of Aviv.

All Feast Days begin at sundown and end at sundown on the day specified in your location.

1 And Yah spake unto Moses and Aaron in the land of Egypt saying,

2 This month shall be unto you the beginning of months: it shall be the first month of the year to you.

3 Speak ye unto all the congregation of Israel, saying, In the tenth day of this month they shall take to them every man a lamb, according to the house of their fathers, a lamb for an house:

4 And if the household be too little for the lamb, let him and his neighbour next unto his house take it according to the number of the souls; every man according to his eating shall make your count for the lamb.

5 Your lamb shall be without blemish, a male of the first year: ye shall take it out from the sheep, or from the goats:

6 And ye shall keep it up until the fourteenth day of the same month