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.
Two of Daniel's prophecies differ by 75 days, perhaps paralleling the 75 dramatic days between the resurrections of Lazarus and Jesus Christ.
Several types of the abomination of desolation have occurred in history, including the desecration of the temple by Antiochus Epiphanes and the Roman legions.
Because of our 'time-bound' state, unless we sync with God's timetable, we are squandering our God-given time to become members of His family.