Theophylact of Ohrid — as excerpted in the Catena Aurea on Mark 13:21-27

“After that the Lord had finished all that concerned Jerusalem, He now speaks of the coming of Antichrist, saying, Then if any man shall say to you, Lo, here is Christ; or, lo, he is there; believe him not. But when He says, then, think not that it means immediately after these things are fulfilled about Jerusalem; as Matthew also says after the birth of Christ, In those days came John the Baptist; (Matt. 3:1) does he mean immediately after the birth of Christ? No, but he speaks indefinitely and without precision. So also here, then may be taken to mean not when Jerusalem shall be made desolate, but about the time of the coming of Antichrist. It goes on: For false Christs and false prophets shall arise, and shall shew signs and wonders, to seduce, if it were possible, even the elect. For many shall take upon them the name of Christ, so as to seduce even the faithful.”