Our Father in Heaven has given a considerable amount of thought and planning into His Day. There are a thousand bits and pieces recorded in Scripture about this event and the resultant aftermath - the restoration of all things - His kingdom. The account given by Jesus, and recorded by Matthew provides us with a very basic timing, and a sequence of events up until the point of His "coming on the clouds" and the "gathering of His elect". He doesn't tell us the exact "day or hour". But He does tell us to "keep watch" and "be ready".

The timing:

Immediately after the tribulation of those days.

He then sets the stage, on a cosmic scale:

‘The sun will be darkened,
     and the moon will not give its light;
the stars will fall from the sky,
     and the powers of the heavens will be shaken.’

Then, "the sign of the Son of Man will appear in heaven"

Hmmm... I wonder what that sign will look like?

We know from Scripture what the response to this sign in heaven will be:

all the tribes of the earth will mourn 

And then what?

they will see this Son of Man coming on the clouds of heaven, with power and great glory.

And then?

He will send out His angels with a loud trumpet call, and they will gather His elect from the four winds, from one end of the heavens to the other.