Three page Excel chart showing the accurate method of calculating the 50 Days of Pentecost starting on Nisan 15, the first day of the Feast of Unleavened Bread, until Pentecost on Sivan 6. Day number one of the fifty days of Pentecost falls on Nisan 16. The Feast of Weeks ends 50 days later on Sivan 6. In 30 AD Nisan 16 was a Sunday and the day of the Resurrection.
The Greek phrase: ‘first of the sabbaths’, found in Matthew 28:1; Mark 16:2, 9; Luke 24:1; John 20: 1, 19; Acts 20:7; and 1 Corinthians 16:2 in the Greek Textus Receptus, is always translated ‘first day of the week’. While it is accurate that the day of the week of the Resurrection is a Sunday, that is not what this phrase means. ‘First of the sabbaths’ refers to day number one of the fifty days of the Feast of Weeks (Pentecost) that ends on Sivan 6. This phrase dates the event of the Resurrection as happening on Nisan 16. In the year 30 AD Nisan 16 and Sivan 6 fell on a Sunday.