Your pants will be ready by three o'clock on Friday the 12th.
We'll have them ready for you by 3pm on the 1st of November.
この場合、次のような言い方ができますよ。
ーYour pants will be ready by three o'clock on Friday the 12th.
「おズボンは12日金曜の3時に仕上がります」
ーWe'll have them ready for you by 3pm on the 1st of November.
「11月1日午後3時までに仕上げます」
ご参考まで!