According to my notes on a technically non-MLP-related project, G5 starts exactly 810 years after G4 ends.
810 years? It fits well with the ponies’ usual pace of technology development, and not too big for an alicorn’s age, which can be counted for centuries. The unveiling of the station hall with intact and functioning machines and the many indications indicate that the disappearance of magic had happened no later than 60 years before Sunny and Izzy met, and the technological gap between the three locations in fact disguised a common technological background. It may also agree with the harmony tree that has been revealed, I do not think it has become less “crystallized” over time, although it has acquired an organic appearance. It is reminiscent of an oak tree that is just as old.
But the indications of what the movie has shown around the tree and the terrain that the Mane 5 walked through - we unfortunately did not see how they got out of Zephyr Heights and down into the valley - are ominous, there is no overgrowth in what was a very fertile and water-rich area that had existed for a very long time, only meadows - which are not naturally created. Only artificial interventions can create such meadows that looked like deserted plains - which is an impossibility in rolling and varied terrain.
There is now a growing probability that the theory that everyone in the valley has been wiped away by what took away the magic may be highly real, and that Ponyville and Canterlot along with Everfree may have existed for over 700 years after the end of the G4 . It is believed that if Sunny were to find what has happened in the valley - there may be no trace left, although Twilight may have left something, as seen with the three crystals.
The catastrophe that hit the Ponykind and now perhaps the whole world if all the magic in the Everfree were used to rib away magic and create memory loss, is at true nuclear level.