Except that the article misses the change from a lunar to a solar calendar. Mark and Luke are ambiguous as to the exact date, but Matthew has the Last Supper taking place in the evening before the Passover lambs were sacrificed. The Jews reckon the day from evening to evening, so the date was 15 Nisan, and it was the night of the first full moon after the vernal equinox. John changes the date of the Crucifixion, purely for theological reasons. The full moon can obviously occur on any day of the week, and since we don't know the year Jesus died, there's absolutely no way to pin it down to an exact date.
