Mt 24:42, 1 Thess 5:2, Rev 3:3, Rev 16:15
The end of the world will come when the gospel is preached all over the world. (Mt 24:14)
Mt 24:14 And this gospel of the kingdom shall be preached in all the world for a witness unto all nations; and then shall the end come.
However, we do not know exactly when world evangelization will occur. So the day of the Lord will come like a thief. We will always have to be awake. (2 Pt 3:10, Mt 24:42, 1 Thess 5:2, Rev 3:3, Rev 16:15)
2 Pt 3:10 But the day of the Lord will come as a thief in the night; in the which the heavens shall pass away with a great noise, and the elements shall melt with fervent heat, the earth also and the works that are therein shall be burned up.
Mt 24:42 Watch therefore: for ye know not what hour your Lord doth come.
1 Thess 5:2 For yourselves know perfectly that the day of the Lord so cometh as a thief in the night.
Rev 3:3 Remember therefore how thou hast received and heard, and hold fast, and repent. If therefore thou shalt not watch, I will come on thee as a thief, and thou shalt not know what hour I will come upon thee.
Rev 16:15 Behold, I come as a thief. Blessed is he that watcheth, and keepeth his garments, lest he walk naked, and they see his shame.