Good Thursday
Remember that the tradition of Good Friday is derived from the notice in Mark 15:42 which reads, “It was Preparation Day, that is, the day before the Sabbath.” An intriguing likelihood raised by John’s chronology is that “the preparation day” of Mark 15 is not necessarily the preparation day for the weekly Sabbath, but rather the preparation day for the High Sabbath of Unleavened Bread. John, in fact, states this explicitly saying, “Now it was the day of Preparation, and the next day was a High Sabbath.” (John 19:31). Since the High Sabbath of the 15th day of Nissan might fall on any given day of the week, the day of preparation before it need not be a Friday. Instead, depending on which weekday the High Sabbath of Unleavened Bread occurred on, the preparation day could be any day of the week.

It is possible that in the year the Master died, the High Sabbath of Unleavened Bread fell on Friday. In that event, Thursday would become the preparation day. Thursday would be the day when everyone prepared to keep the Sabbath of Unleavened Bread. Therefore, Thursday would have been the day of the crucifixion. It would be Good Thursday, not Good Friday. Not only would that circumstance allow for each of the above cited Sabbath objections to be met, but it amazingly allows for a more realistic three days and three nights in the tomb, a total span of 49-57 hours.

Read the details at:

http://www.bethimmanuel.org/articles/passover-and-passion-chronology