Chazal’s timeline works out perfectly:
Avraham was born in 1948 and had Yitschak in 2048.
There were 400 years until freedom from Egypt (2448) and another 480 until the first Beit Hamikdash was built in 2928.
We are in 5772 and the 2nd Temple was destroyed in (about) 69 AZ, which was 1943 years ago, so the 2nd Temple was destroyed in the year 3829.
The first Temple stood for 410 years and the second for 420 (see first perek of B”B) and there was 70 years of exile in between. That’s a total of 900 from the beginning of the first to the end of the second.
Start with the beginning of the first, in 2928, and add 900, you get 3828 – which everyone agrees to as the end of the second Temple (give or take one year – but one out of 5772 is close enough).