If Jesus was crucified on April 3rd, 33 AD and was 30 years old at that time, you can calculate his birth year by subtracting 30 from 33. This means he would have been born in 3 BC.
Since he was 30 years old at the time of his crucifixion, we can assume he had not yet reached his 31st birthday by April 3rd. Therefore, if we take the year of his birth as 3 BC, and considering he was born likely in the same month as he was crucified (April), we could estimate his birthdate to be sometime in late March or early April, but exact day and month details are not specifically pinpointed in historical texts.