John 19:31 The Jews therefore, because it was the preparation, that the bodies should not remain upon the cross on the sabbath day, (for that sabbath day was an high day,) besought Pilate that their legs might be broken, and that they might be taken away.
"for that sabbath day was an high day"
It was the special sabbath of the passover feast, an high day. Any day of rest in Jewish feast days was called a sabbath, no matter what day of the week it fell on. The high day sabbath associated with the death of Jesus was a Thursday.
Crucified on the preparaton day, Wednesday the 14th day of the month Nisan.
Followed by the passover and the day of unleavened bread which happened in that year on the 15th day of the month Nisan. That was not the usual weekly sabbath.
Exodus 12:3 Speak ye unto all the congregation of Israel, saying, In the tenth day of this month they shall take to them every man a lamb, according to the house of their fathers, a lamb for an house:
Exodus 12:6 And ye shall keep it up until the fourteenth day of the same month: and the whole assembly of the congregation of Israel shall kill it in the evening.
Exodus 12:16 And in the first day there shall be an holy convocation, and in the seventh day there shall be an holy convocation to you; no manner of work shall be done in them, save that which every man must eat, that only may be done of you.
[That is the first day of the feast, not the first day of the month. The lamb was killed on the 14th day of the month in the evening (which is Tuesday night [Jewish Wednesday] when Jesus ate the passover with the disciples]; Jesus was killed on Wednesday the 14 th day of the month. You see, no manner of work done on the first day of the feast; that is the high day sabbath. It was on the 15th day of Nisan, following the preparation day. Any day of rest is called a sabbath. ]
Passover and feast of unleavened bread, on 15th day Nisan, Thursday, the first day of the feast, which is a day of rest or high sabbath.
Exodus 12:17 And ye shall observe the feast of unleavened bread; for in this selfsame day have I brought your armies out of the land of Egypt: therefore shall ye observe this day in your generations by an ordinance for ever.
Exodus 12:18 In the first month, on the fourteenth day of the month at even, ye shall eat unleavened bread, until the one and twentieth day of the month at even.
They had the Lord's Supper at night on Tuesday the 14th day of the month [which was the beginning of the Jewish Wednesday]. Jesus was apprehended for a night trial. He was brought before Pilate in the daylight hours of the 14th which is still Jewish Wednesday. They wanted Him off the cross by Nisan 15, a day of rest or Sabbath, making the first day of the feast. [Nisan 15 started at Wednesday 6:00 pm.]
Go to this website and read about it in detail:
http://www.tne.net.au/~abdaacts/3d3n.html