This is all irrelevant. Luke records that Sunday (the first day of the week) was the 3rd day from all the events of the crucifixion. If Sunday is the third day, and Wednesday is the crucifixion day, then that means Jesus was taken into custody Tuesday night. That's 5 days and nights in the heart of the earth and 5 days since the crucifixion.
If Wednesday is the crucifixion day, Jesus was "in the heart of the earth" for 5 days and night"? Sorry, I can't even begin to see any reason is that.
Going backwards:
Saturday night
Saturday day
Friday night
Friday day
Thursday night
Thursday day
That's three days and three nights. But we know Jesus wasn't in the tomb starting in the morning, as he was only put there at sunset. We don't know he was in the tomb Saturday night. So, strike Saturday night and add in Wednesday night, and we get to three days and three nights.
To answer the OP, Saturday was the third day. But, Sunday morning is when the tomb was discovered empty.
I think Thursday is also a fair answer. You'd have to count time on the cross as a day in the heart of the earth, but he didn't die until evening. This would make Sunday the third day. I'm also doubtful that the Jews would plan two sabbaths in a row (Friday high sabbath plus Saturday).