Is the Hadith that states there will be seven years between the conquest of Constantinople and the major battles (Al-Malahim Al-Kubra) authentic, especially since Constantinople was conquered about six centuries ago and the major battles have not yet occurred?

The hadith (definition) referred to is, "Between the great battle and the conquest of the city are six years, and the Dajjal will emerge in the seventh." This hadith has been deemed weak by scholars of hadith. It is established that Constantinople will be conquered before the Hour, and that seventy thousand from the Children of Isaac will invade it, causing its sides to fall by takbir (proclaiming God's greatness) and tahlil (proclaiming God's oneness). They will then enter it and take spoils. While dividing the spoils, the Dajjal will emerge. The city mentioned is Constantinople, which was conquered through battle by Sultan Mehmed the Conqueror. However, its conquest without battle has not yet occurred and will occur as the Prophet, peace and blessings be upon him, foretold.