What does the 'great' sabbath in John 19:31 mean?

John 19:31 uses an adjective for the Sabbath that appears nowhere else in the New Testament:

"For the day of that Sabbath was great (megale, G3173)." — John 19:31

Every other Sabbath in the Gospels is just the Sabbath. This one is "great." Both the Thursday and Friday crucifixion positions have to explain what made it great — and the answer comes down to the Jewish festival calendar.

The Thursday position says the "great" Sabbath was the festival Sabbath of Nisan 15 — the first day of Unleavened Bread, which Leviticus 23:7 designates as a holy convocation (miqra-qodesh, מִקְרָא־קֹדֶשׁ, H4744+H6944) requiring rest from servile work. On the Thursday reading, Nisan 15 fell on Friday and the regular weekly Sabbath fell on Saturday — two Sabbaths back to back. The "great" day was the festival one. This also gives a natural explanation for a small puzzle in the Gospels: Mark 16:1 says the women bought spices after the Sabbath, but Luke 23:56 says they prepared spices and then rested on the Sabbath. Two Sabbaths in a row provide a gap day between them — the women bought spices Friday evening (after the festival Sabbath ended), prepared them the same day, then rested on Saturday.

The Friday position says if the crucifixion was on Friday (Nisan 14), then Saturday carried both the weekly Sabbath and the Nisan 15 festival Sabbath on the same day. A day with double sanctity — both designations falling together — would naturally earn the adjective "great." Astronomical reconstruction shows that in both AD 30 and AD 33, Nisan 14 fell on Friday, which means Nisan 15 and the weekly Sabbath coincided on Saturday.

The text only says the Sabbath was great, not why. Both explanations are inferences from the Torah's festival calendar. The study works through the full evidence for both positions and shows where each one is stronger or weaker. For the full analysis, see Three Days and Three Nights.