I have been doing Passion to Know More for over six years. For the most part I write about what I'm studying in the Bible. By far my most popular article is What Hour is That? which is about the difference between how the Jewish people and the occupying Romans measured the hours in the New Testament. There are many places where it will say for example "the third hour" or "the sixth hour." I was explaining what that meant. I also went over how the Jewish people divided night watches into thirds and Romans divided night watches into fourths. I got quite a bit of feedback on the article finding it quite helpful, but one thing some people asked about was Jesus being crucified on Good Friday and resurrected on Easter Sunday; how can that be the third day and about Mary Magdalene and the women coming to the tomb on the first day of the week.
Today we measure days and hours by Roman way - the day begins at midnight and is broken up into two 12 hour segments; midnight to noon is am and noon to midnight is pm. But that isn't how the Jews in biblical times counted their days and hours.
The Jews began counting a 24 hour day at sundown which would obviously vary time-wise. I used 6pm which is what others use to explain this. They broke it up into 12 hour segments too, but called these nighttime - from sundown to sunrise (6pm to 6am for our purposes) and daytime - sunrise to sundown (6am to 6pm for our purposes.)
It seems to us by the way we measure hours and days that Jesus died on Good Friday and rose on Sunday would be two days (less than 48 hours), not three days. But remember the Jews started their 24 hour day at sunset. The gospels tell us Jesus died about the ninth hour (Jewish way of counting hours because the authors were Jews) which would be Jewish daytime or about 3pm for the Roman way of counting hours.
Now from the sixth hour darkness fell upon all the land until the ninth hour. About the ninth hour Jesus cried out with a loud voice,... Matthew 27:45,46.
And Jesus cried out again with a loud voice, and yielded up His spirit.
The first day started at 6pm on Thursday. Jesus died around 3pm on Friday - the way we measure hours today. That is still the first day.
6pm Friday to 6pm Saturday would be the second day.
Jews would measure the third day from 6pm on Saturday night to 6pm Sunday night.
Jesus rose on Sunday because the tomb was sealed as the Roman guard kept watch during the night, but in the morning of the first day of the week (which started Saturday night at 6pm and is still a 24 hour day) Mary came to the tomb.
Now after the Sabbath, as it began to dawn toward the first day of the week, Mary Magdalene and the other Mary came to look at the grave. Matthew 28: 1
The Sabbath is the seventh day of the week and for the Jews began at sundown (6pm for our purposes) on Friday night and ended at sundown on Saturday night. The empty tomb was discovered "after the Sabbath" as it became dawn the first day of the week, i.e. Sunday.
Day 1 - Thursday 6pm - Friday 6pm. Jesus died on the ninth daytime hour or about 3pm Friday according to the biblical text, but it is still the first day.
Day 2 - Friday 6pm - Saturday 6pm.
Day 3 - Saturday 6pm to Sunday 6pm. Empty tomb discovered around 6am (Roman time) on Sunday - the third day.
I hope that clarifies it for you.