Actually Jesus had no idea when the parousia would occur.
It would take place at a time that no one could anticipate as opposed to his coming in judgment against Jerusalem the timing of which could be anticipated to the day and from which one could escape, hopefully not on a Sabbath when the city gates would be locked.
Jesus's coming in judgment in 70 A.D. was to be local (Jerusalem Judea and fields surrounding) whereas the parousia was to become a trap for the whole world and precipitate the final judgment...sheep and goats, good servants and bad etc.
The judgment on Jerusalem was to be preceded by signs on abnormal times and followed by slayings and deportations to far off nations whereas the parousia could not be fled from, people would be taken from their beds and from their places of work during normal times.
There is more but typing on my cell is tiresome