John Gill Commentary Ezra 6:15

"And this house was finished on the third day of the month Adar, which was in the sixth year of the reign of Darius the king." — Ezra 6:15 (ASV)

And this house was finished on the third day of the month
Adar
The twelfth month of the year with the Jews, and answers to part of our February and part of March:

which was in the sixth year of the reign of Darius the king ;
four years after the decree came forth.