Perspective is important to identifying patterns. If we look down a road to the distant horizon we can see the road “vanishing” into the distance. This is known as the vanishing point. If we stand directly in front of a road sign we might not see the signs lying behind because our view is blocked but if we shift our viewpoint the new perspective reveals a number of road signs trailing into the distance.
Similarly, “The day of the Lord” is an “eschatological day” that punctuates the equilibrium of history. It is not a single day but rather the in-breaking of divine sovereignty in history that cumulatively forms “The Day of the Lord” until such time that it is revealed in its fullness. The Bible indicates this through typology – i.e., the Egyptian Passover Exodus, the Passover deliverance of Hezekiah and the Passover crucifixion are all part of “The Day of the Lord”. In similar fashion 70 CE and 135 CE is also the “Day of the Lord” as they allowed for repentance and the return of the messiah but only if the national response was correct. Otherwise, “The Day of the Lord” became a “Day of Judgement”; “Woe unto you that desire the day of the Lord! to what end is it for you? the day of the Lord is darkness, and not light (Amos 5.18).