The Bible tells us it is a memorial of blowing of trumpets. The event this reference is one we are told many times not to forget – the day the Almighty shouted down the 10 commandments to the people from atop Mount Sinai in the desert after delivering them from slavery in Egypt.
It also heralds the Messiah’s second coming in prophecy (during which he will fulfill all the fall feasts just as he fulfilled the spring feasts at his first coming).