End of the Age and Christ's Return

The sign of the end of the age comes right before the sign of Christ's return.  These are two distinct signs.

• End of the Age: sun, moon, and stars go dark.
• Christ's Return: He will come on the clouds of the sky with power and great glory.

From The Sign by Robert Van Kampen

Sign of the End of the Age 
The cataclysmic and terrifying changes in the sun, moon, and stars, when all the natural lights of the world will be extinguished, plunging the earth's atmosphere into total darkness.  This sign will accompanied by worldwide earthquakes, most likely destroying all man-made light sources on earth, and will occur at the opening of the sixth seal, immediately before the sign of Christ's second coming is seen by all the inhabitants of the world.

Matthew 24:29
But immediately after the tribulation of those days the sun will be darkened, and the moon will not give its light, and the stars will fall from the sky, and the powers of the heavens will be shaken.  And then the sign of the Son of Man will appear in the sky, and then all the tribes of the earth will mourn, and they will see the Son of Man coming on the clouds of the sky with power and great glory.  And He will send forth His angels with a great trumpet and they will gather together His elect from the four winds, from one end of the sky to the other.