They will fall by the sword and will be taken as prisoners to all the nations. Jerusalem will be trampled on by the Gentiles until the times of the Gentiles are fulfilled.
Luke 21:24
The “times of the gentiles” began when Jerusalem was trampled on by the Gentiles in 70AD, right after its time of destruction (see Luke 21:20-23 for context). This proves the time gap described by “Eutheos” in Matthew 24:29 (see here for further context), and, since Jerusalem is yet trampled down, we understand that it continues even up to the current time.
Jesus said that the city would be trampled until this time was fulfilled. We will know, then, that this time is completed, when the Jews are once again in control of the city. This may or may not be in connection with the timing of the second coming, also described in Luke 21 and Matthew 24, but all we know is that when this time is fulfilled, it is then that the city will be fully restored.