And he shall speak great words against the most High,
and shall wear out the saints of the most High,
and think to change times and laws:
and they shall be given into his hand until a time and times and the dividing of time.
Daniel 7:25 (1260 days/years) 538 A.D. - 1798 A.D.
"Three important issues are present which point to 538 AD:
1) Justinian's decree, found in the Code of Justinian, that the bishop of Rome be the supreme head over all the churches, definer of doctrine and corrector of heretics. This happened around 534 AD
2) This decree, although promulgated, could not be given effect immediately, because several very strong groups warred against the bishop of Rome, including the Ostrogoths, the Vandals and the Heruli. The first two groups were dealt with, however, the Ostrogoths besieged Rome in 537, with the pope inside the city walls. Thus, the pope was effectively imprisoned by the Ostrogoths, who certainly were intent on overthrowing him. But in 538, Belisarius lifted the siege of Rome and the pope was rescued. In that year, also, Justinian replaced the deposed Silverius with Vigilius as the new pope, and gave him military protection. Thus the 'teeth' in the decree and the church-state alliance made real.
3) The Ostrogoths did not quit. A few years later, they sacked Rome, but the pope had fled to another location, thus did not lose his power. Shortly after that time, the Ostrogoths disappeared from history.
4) Centuries later, Napoleon took away by decree, the pope's authority and power to persecute. A few years later, the papal estates were restored, but not the persecuting power or the power over doctrine for Christendom. This was made effective in 1798 when Napoleon's general took the pope captive. Belisarius basically enforced Justinian's decree and Napoleon's general made it null and void."
Well put by reddogs via Adventist Forum (2008)
Click below for a pop-up detailed explanation of the time frame