The Messenger of Allah ﷺ said, "The great battle, the conquest of Constantinople, and the emergence of the Dajjal will all occur within seven months."
حدثنا عبد الله بن محمد النفيلي حدثنا عيسى بن يونس عن أبي بكر بن أبي مريم عن الوليد بن سفيان الغساني عن يزيد بن قتيب السكوني عن أبي بحرية
قال رسول الله ﷺ الملحمة الكبرى وفتح القسطنطينية وخروج الدجال في سبعة أشهر
Its isnad is daif. Tirmidhi narrated it in the Book of Tribulations, chapter on what has been said about the signs of the emergence of Dajjal, hadith 2238, and Ibn Majah narrated it, hadith 4092, from the hadith of Abu Bakr bin Abu Maryam, and he is daif and had become mentally confused. Yazid bin Qutayb is of unknown status.