MATTHEW 24 and LUKE 21 ARE BOTH DESCRIBING THE  VERY THE SAME EVENTS.....

Matthew 24 and Luke 21 are BOTH recorded individual versions of the Lord's Olivet Discourse, but Luke is a more detailed version .

Matthew 24:29 states:

".....shall the sun  be darkened, and the moon shall  not give her light,  and the stars shall fall from heaven...."

Luke 21:25 states:

"And there shall  be signs in the sun, and in the moon, and in the stars...." 

It is obvious that these two preceding Scriptures are BOTH describing the very same 'point in time' in the Lord 's timeline of end-time events . Likewise, the following two Scriptures are also BOTH describing the very same 'point in time' in the Lord's timeline of end-time events which occur IMMEDIATELY BEFORE "the sun be darkened,  and the moon shall not give her light, and the stars shall fall".

Matthew 24:21  states :

"For then shall   BE GREAT TRIBULATION...."

Luke 21: 23

"For there shall  BE GREAT DISTRESS in the LAND, and wrath upon this PEOPLE." 

( "great distress" = great tribulation  )  ( "in the land" = the land of Israel )  ( "upon this people" = the people of Israel )  

It is obvious that these two preceding Scriptures are BOTH describing the very same 'tribulation event' that is the Gog-Magog War which is exclusively upon the land and upon the people of Israel, and NOT UPON THE WHOLE WORLD . Notice that this tribulation event which is exclusively upon Israel occurs IMMEDIATELY BEFORE the resurrection / rapture which BEGINS with the "signs in the sun, and in the moon, and in the stars ". 

SO, THERE YOU HAVE IT :

Matthew 24:29 states :

"Immediately AFTER the tribulation  OF THOSE DAYS....." then the resurrection / rapture happens according to Matthew 24:30-31. 

The phrase, "of those days" is referring to "the days are coming" of the Gog-Magog War of tribulation judgment that is exclusive to the land and the people of Israel, BEFORE THE RAPTURE, which Jesus warned the Jews of in His last prophecy according to : Luke 23:28-31. Therefore, the sequence of end-time events are as follows: 

The days of the Gog-Magog War come upon Israel...... followed immediately by the resurrection / rapture .......followed by the great tribulation upon the whole world. 

According to Your Holy Word, come Lord Jesus !