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Ah, I don't think I ever got around to actually watching that episode, so I forgot that one.
Also, I sort of default to the assumption that if it isn't mentioned in the series it probably didn't happen, so generations one to three don't really count.
But anyway. Three canonical holidays tied to ancient disasters, two of which seemed to primarily affect pony civilisation rather than nature itself. And Discord, whose stuff is reversed by the same blast that petrifies him.
Either the Little Ice Age caused by the Windigo had
huge knock-on effects, or things have always been this way.
(Of course, if it turns out there was some epic hypercatastrophe that broke reality, I'll withdraw this assertion, but so far there's been no hint of one that actually counts.)