Charles Ellicott Commentary Zechariah 8:19

"Thus saith Jehovah of hosts: The fast of the fourth [month], and the fast of the fifth, and the fast of the seventh, and the fast of the tenth, shall be to the house of Judah joy and gladness, and cheerful feasts; therefore love truth and peace." — Zechariah 8:19 (ASV)

The fast of the fourth [month]. —The LXX, after the analogy of Genesis 1:31, renders the fourth fast, and similarly with the others.