Some scholars doubt that what Christians call the "Last Supper" was a seder. Here is the Netzarim timetable for what happened to Ribi Yehoshua.
SEDER: Nisan 15, Yom Khamishi or the fifth day of the week (but Wednesday evening on the secular calendar before midnight). The arrest happened after the seder.
TRIALS, TORTURE, ETC. Nisan 16-19, all during the next week.
EXECUTION AND BURIAL: Nisan 20 (the third day of the following week or Tuesday on the secular calendar). Execution began in the AM, burial occured before sundown, as was necessary to accomodate Jewish law, the next day being the seventh day of Pesach and a shabbaton. (Christians interpreted the Preparation Day and the Sabbath as a reference to the seventh day of the week. This is the source of a timetable mistake.) All the stuff that was supposed to have happened to Ribi Yehoshua could not have happened overnight on a yom tov, even allowing for the fishiness of the Temple kohanim and Herod.
DISCOVERY OF THE MISSING BODY: Nisan 25, motzei shabbat or after dark on what would be Saturday evening on the secular calendar. Christians interpreted reference to twilight as "dawn" in the morning. More naturally, women went to the tomb at first chance after shabbat ended with spices etc. So whatever happened to account for a missing body happened on shabbat.
This is the only timetable that seems to make sense viz. Jewish law and dates the year. The Christian timetable was designed to accommodate the substitution of Sunday for shabbat and makes little logical sense. Much more information in the Netzarim Reconstruction of Matiytyahu. See Schueller House.