The phrase "of that day and hour knows no man" is a Hebraic idiom that referred to the Feast of Trumpets on the 1st of Tishri. Because the feast was held on the first day of the month, they could not know in advance which day would be sanctified by the Council. So, they had to wait for the Council (Sanhedrin) to sanctify it after having the report of the two witnesses for the new moon.
That is why the Jews had to plan the feast in advance, so the Council declared the first day of the new month, then they could begin the feast.
Reading and understanding the English words does not covey the imagery of the Hebrew customs and feast days. But, when Christ said those words to His disciples they immediately associated the warnings for the destruction of the temple with the Feast of Trumpets on the first of Tishri because they recognized the language of the feast day.
Contrary to what most English reading students of the Bible believe, Christ told His disciples the time of His return. He returned in judgment against those who had crucified Him, and were persecuting His saints in the destruction of that city and temple which had become desolate in the 1st century AD, specifically AD 70.
Matt. 24 was discussing the destruction of the temple, not the end of the world!
So, there is no reconciliation necessary with Amos 3:7. The prophets and Christ told them what to expect. They didn't know which year that judgment was coming, but they knew the time. They knew the "last trump" associated with the last trump of the Feast of Trumpets was judgment day, also called Yom Hadin. First of Tishri.
Christ did not leave them guessing. See more scriptural proofs in the posts at my blog, ShreddingTheVeil.org:
Signs of the Feasts- Part I: Christ Told the Pharisees...here
Signs of the Feasts - Part II: Christ Told His Disciples... here
Signs of the Feasts - Part III: The Thief in the Night here