The formula 'the coming of the Son of Man' is code for 'the Day of the Lord.' The formula does not refer to the fall of Jerusalem in 70 AD, but the days ahead.
The references to trumpets suggest an announcement of a specific event or an alarm of what is to follow. Typically, the events themselves are figurative trumpet blasts.
Only the Father knows the precise time of Christ's return, but the message to all Christians is to be vigilant and busy overcoming that we may see Him in glory.
The Feast of Trumpets memorializes God's deliverance of Israel beginning with Joseph, and looks forward to Christ's return when God will deliver His people.
We cannot allow ourselves to become surfeited with the world's distractions, being lulled off to sleep as the foolish virgins, wasting our precious time.