It's fairly well known that there's an apparent discrepancy in the Easter story: Jesus is killed on Friday, spends 3 days in the tomb, and is resurrected on Sunday.
Here's Jesus describing his impending death in Mark 8:31:
So it seems like Jesus expected his resurrection to be three days after his death on Friday, which would mean Monday, surely? No, not actually. This is a misunderstanding of what is going on: days are being counted, rather than a length of time being measured. The first day is Friday, the second Saturday, and the third Sunday. This seems rather unusual to those educated in Western mathematics, but was and is fairly common practice in other times and places.
One fascinating example is traditional East Asian age reckoning, where a person's age is given as the counted years a person has been alive in. So for example, if someone was born on December 31, 2000, then on January 1, 2001, they would already be called 2 years old, as they had lived in 2 years, 2000 and 2001. This is the difference between counting and measuring.