Is Passover 7 days or 8 days?

According to the instructions in the Torah, the Passover festival lasts for seven days.

Each family brings the Paschal lamb sacrifice to the Temple, and eats it there, on the

first day, and refrains from eating any leavened products for the rest of the 7 days.

Judging by the use of the past tense in the question, it may surprise you to learn that

right now, today, in 2013, the Passover is still observed throughout the Jewish world,

with two primary modifications: First, the Paschal lamb sacrifice is not offered, because,

just now, there is sadly no Temple in which to offer it. Second, for very technical reasons,

the festival is observed for eight (8) days by Jews outside of Israel.

Answer:

Both. The Torah calls it both one day (Leviticus 23:5) and one week (Leviticus 23:6). The one day refers to the offering up of the Passover sacrifice, while the full week is the complete festival. Note that the Passover sacrifice was offered up on the day before the full festival (unlike what the above answer implies). The day before Passover, while not a complete day of rest, was observed (Talmud, Pesachim 2b) as a minor festival (comparable to Purim, Tisha B'Av and Hol HaMoed, which have a partial cessation from work). The offering was brought on the afternoon of that day and was eaten that night, the first night of the full Passover festival itself.