The word Elohim is plural. Eli or Eloi is “my God” in the singular. They had never heard it in the singular, so they thought Jesus called for Elias!
This was the moment when Jesus became sin for us.
Jesus was the Passover lamb, sacrificed outside the camp on Golgatha. The veil that separated the holiest area from the rest of the temple was rent from top to bottom to signify the end to all offerings. Jesus was offered once for all time.
This was now late on 14th of Nisan, the Passover.
It is now Thursday afternoon, and the next day is a special Sabbath. Then comes the normal Sabbath on Saturday. This is not all that uncommon, it happens every seventh year on average, and this was the case in A.D. 30. The preparation means to prepare meals for two days as well as the passover meal before sunset. ( https://lenbilen.com/2017/04/14/when-was-the-crucifixion-of-jesus/ )