You're contradicting yourself, better find another term to define a calendar day. They bought spices on Sunday, the same spices which they bought BEFORE Sabbath. Nowhere does it suggest that two sabbaths were not back to back.
Nope, there was a high Sabbath on Thursday. The women bought spices on Friday. The women could not come to the tomb on Saturday the weekly Sabbath but had to wait until the first day of the week, Sunday. The third day would be on Saturday right before 6pm (which would be the beginning of Sunday). What Jesus did for those 12 hours is a mystery. He had already been risen when the women showed up at the tomb. He may have stayed in the tomb a while and prayed. That's all speculation.