It depends on what program it is.
Most top ecology and biology programs have deadlines in early December.
Most top-20 physics and astronomy programs (excluding Columbia) have deadlines on December 15th. Columbia's deadlines are usually on the first few days of January. Mid-tier astronomy programs tend to have deadlines around January 15.
That said, there are weaker programs in Physics (like Montana State and Kansas) that have deadlines that go well into Spring.
As for most strong Earth/Atmospheric/Planetary science programs - they primarily have deadlines in late December and early January.
(E.g. for this year for EAPS programs - deadlines were Stanford in mid-December, Berkeley on Dec 19, Harvard/Princeton on Dec 31, Caltech on Jan 1, Yale on Jan 2, Columbia on Jan 4, MIT on Jan 5, Chicago on Jan 9, UWash+Brown on Jan 15, and Cornell on Feb. 1st).
As for my case, I was utterly unprepared until mid-December.
I didn't take my General GREs until mid-December (though I took the Biology GRE in mid-October and the Physics GRE in mid-November - those two dates are the two subject GRE test dates in autumn), and only asked for LORs in mid-December (I managed to get them all in by January 2, but a couple of professors said that they wouldn't be able to write me LORs because they would be traveling during late December - I was fortunate to have many options to choose from though). Then I didn't start on my personal statement until the last two weeks of December (and I went through like 7-8 proofreaders). So the result was that I missed the Harvard/Princeton deadline and barely made the Caltech deadline with a crappy essay. Everything past January 2 was fine though.