How do we know Christ's coming is a past event?

Christ made a clear declaration in Mark 13 that the events He predicted would occur within the lifespan of His contemporaries. The phrase 'this generation shall not pass until all these things be fulfilled' serves as a pivotal statement indicating that His coming and the associated judgments were realized during their lifetime, particularly culminating in the historical event of Jerusalem’s destruction in A.D. 70. This understanding aligns with the concept that Jesus himself initiated the new covenant, bringing a paradigm shift from the previous covenant with Israel to His established kingdom.