Oh, I get it, you think it must be on an "appointed feast". Well according to the source, it's pretty straightforward, it's gonna be on a feast of the trumpet because of the phrase no man know the day.... and in shmita year with major astronomical events appearing on Festival Days (i.e. Passover and Tabernacles).
From wiki
"Four times in the year the world is judged: On Passover a decree is passed on the produce of the soil; on Shavuot, on the fruits of the trees; on Rosh Hashanah all men pass before Him ("God"); and on the Feast of Tabernacles a decree is passed on the rain of the year.
In Jewish thought, Rosh Hashanah is the most important judgment day, on which all the inhabitants of the world pass for judgment before the Creator, as sheep pass for examination before the shepherd.
Another source
The first four of the seven feasts occur during the springtime (Passover, Unleavened Bread, First Fruits, and Weeks) and they all have already been fulfilled by Christ in the New Testament. The final three holidays (Trumpets, The Day of Atonement, and Tabernacles) occur during the fall, all within a short fifteen-day period.
Many Bible scholars and commentators believe that these fall feasts have not yet been fulfilled by Jesus. However, the “blessed hope” (Titus 2:13) for all believers in Jesus Christ is that they most assuredly will. As the four spring feasts were fulfilled literally and right on the actual feast day in connection with Christ's first coming, these three fall feasts, it is believed by many, will likewise be fulfilled literally in connection to the Lord's second coming.
Yup, definitely feast of trumpet.
