Matthew 24 is difficult: both difficult to interpret, and difficult to ignore. Although some details puzzle me (and I welcome your feedback), I am convinced that many people greatly abuse the clear parts. How can futurists justifiably push it all into our future? How can full preterists justifiably push it all into our past?
Jesus is talking about two totally separate events. Consider the contrasts He provides. Regarding the destruction of Jerusalem, Jesus foretold a clear sign of impending doom. As for the end of heaven and earth, Jesus said nobody knows when it will be.
The sign of Jerusalem’s end was “the abomination of desolation, spoken of by Daniel,” to which the Holy Spirit adds, “(whoever reads, let him understand)” (Matthew 24:15). Luke offers the understanding: “When you shall see Jerusalem compassed with armies, then know that the desolation thereof is nigh. Then let them which are in Judea flee” (21:20,21). Escape was offered.
In sharp contrast, Jesus said: “Heaven and earth shall pass away… but of that day and hour knows no man” (Matthew 24:35,36). I believe that both preterists and futurists empty these words of meaning. Preterists say the general time of Jerusalem’s destruction was known, but not the exact day. Futurists say we know roughly when Jesus will return; we just don’t know the exact day. They both miss how Jesus was contrasting two events.
Jesus gave them a precise sign so they would know exactly when to run for their lives to escape Jerusalem’s doom. In contrast, no warning sign will be given of Jesus’ return. “In such an hour as you think not the Son of man comes” (Matthew 24:44). From Matthew 24:35 thru 25:13, Jesus’ theme is that we must always be ready because there is no way to know when He will return. No sign will allow unbelievers to quickly repent and escape doom.
No one knows when Jesus will return, either roughly or precisely.