Year numbers are ordinal. It is the 2020th year, therefore it is at the end of the year that 2020 years will have elapsed in the "Current Era".
2020 May 29
go back 2019 years
AD 1 May 29 (I know, I am ignoring the change from Gregorian to Julian)
There was no year 0. Go back one year, from AD 1 to
1 BC, May 29 (that was 2020 years ago)
go back a further 1480 years
1481 BC, May 29
Of course, there was no such thing as a "month of May" back then.
Other than Egyptians, most everybody else was on a lunar calendar, where months begin either at the New Moon or the day after.
In one commonly used Hebrew calendar (which may have been used back then), it would have been the 8th day of Sivan, in the year 2280.
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If you find a coin bearing the date "1481 BC", it is a fake.