The first day of the feast of unleavened bread was considered a Sabbath, as were many of the Jewish feasts. A careful study will show that days declared by God to be a Holy Convocation where they are directed to do No Servile Work, were, or could be, considered a Sabbath.
Examples:
Lev. 16:30-31: For on that day shall the priest make an atonement for you, to cleanse you, that ye may be clean from all your sins before the LORD.
It shall be a sabbath of rest unto you, and ye shall afflict your souls, by a statute for ever.
Leviticus 23:39: Also in the fifteenth day of the seventh month, when ye have gathered in the fruit of the land, ye shall keep a feast unto the LORD seven days: on the
first day shall be a sabbath, and on the eighth day shall be a sabbath.Now, it is true that the bible does not say specifically that Passover or the Feast of Unleavened bread are "Sabbaths", but the conditions for celebration are identical.
I am sure the ancient Hebrews, in their own way, would ascribe to the concept that, "If it walks like a duck and quacks like a duck, it must be a duck." Or, "If it looks like a sabbath, and sounds like a sabbath, it must be a sabbath."
Otherwise, you are left with a big job of explaining, in a rational way, how Friday is the burial day.
If you believe that Friday is the day, how does He fulfill the sign of the prophet Jonas, or His declaration that if they should destroy "this temple, in three days I will raise it up again."This he spoke about his body.
Either He laid three days in the grave as He said, or He didn't. He fulfilled His own prophecy or He didn't.
Avoid the Trick Day Counting explanation. If you don't, you will need to explain why there are 730 day in a year.