The Prophet ﷺ said: The greatest war, the conquest of Constantinople and the coming forth of the Dajjal (Antichrist) will take place within a period of seven months.  

قَالَ رَسُولُ اللَّهِ ﷺ الْمَلْحَمَةُ الْكُبْرَى وَفَتْحُ الْقُسْطَنْطِينِيَّةِ وَخُرُوجُ الدَّجَّالِ فِي سَبْعَةِ أَشْهُرٍ  

The Prophet ﷺ said: The time between the great war and the conquest of the city (Constantinople) will be six years, and the Dajjal (Antichrist) will come forth in the seventh. Abu Dawud said: This is sounder than the tradition narrated by Isa (bin Yunus)  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ بَيْنَ الْمَلْحَمَةِ وَفَتْحِ الْمَدِينَةِ سِتُّ سِنِينَ وَيَخْرُجُ الْمَسِيحُ الدَّجَّالُ فِي السَّابِعَةِ