John Gill Commentary Esther 8:12

"upon one day in all the provinces of king Ahasuerus, [namely], upon the thirteenth [day] of the twelfth month, which is the month Adar." — Esther 8:12 (ASV)

Upon one day, in all the provinces of King Ahasuerus, namely,
upon the thirteenth day of the twelfth month, which is the month Adar .
] The day appointed and fixed in the former letters for the destruction of the Jews, (Esther 3:13) .