Did Jesus lie about how long he would be buried?
Before his crucifixion, Jesus said that “As Jonah was in the belly of the great fish for three days and three nights, so will the Son of Man be in the heart of the earth for three days and three nights” (Matthew 12:40) But this poses a problem because, according to the Bible, Jesus was not buried for a full 72 hours. So how do Christians deal with this fact? Josh McDowell, author of “The Bible Handbook of Difficult Verses,” explains this perplexing puzzle.
…Jesus was crucified in the daytime on Friday, dying before sundown, spent Friday night, all day Saturday, and Saturday night in the grave. He rose sometime before early morning on Sunday. That only accounts for two full nights and two partial and one full days. How can Jesus’ statement be accurate?
Under Jewish calculations a period of light and darkness constituted a “day.” And any part of a “day” was considered a whole day. So Jesus didn’t mean he would be in the tomb 72 hours. The fact that he was dead and buried on part of Friday, all of Saturday, and part of Sunday meant that period was considered three days. Calculating days in this fashion is borne out in Genesis 42:17; 1 Samuel 30:12-13; Esther 4:16 and 5:1.
(http://goo.gl/5NblhI, p. 192)