What counting system was used in the gospels? Jesus said that he would be raised on the third day; if he was crucified on Friday, is 3 days later Monday not Sunday?

Many ancient cultures used inclusive counting, so Jesus would have been crucified on Day 1. In modern-day counting, exclusive counting is often used, where the current day is Day 0, not 1.

However, many traditions still adopt inclusive counting, such as the number of days in a wake/at a funeral for Chinese families.