The 1,290-day and 1,335-day time periods refer to events that will happen in this generation. Each period begins with a significant prophetic event.
Before Christ's return, the Two Witnesses must appear, the Beast and False Prophet must arise, and daily animal sacrifices must be re-instituted in Jerusalem.
We need to emulate Daniel by faithfully studying and praying for understanding, asking God for what He has promised and for His will to be done.
Several types of the abomination of desolation have occurred in history, including the desecration of the temple by Antiochus Epiphanes and the Roman legions.
Two of Daniel's prophecies differ by 75 days, perhaps paralleling the 75 dramatic days between the resurrections of Lazarus and Jesus Christ.