> you might see "the last quarter of the second millennium BC", which means minus 2000 to about minus 1750.
From comparing some online answers (see links), I'd conclude that even though the numbers are ordered backward, "first"/"last"/"early"/"late" would more commonly be understood to reference the years' relative position in a timeline. That is, "2000 to about minus 1750" would be the first quarter of the second millennium BC.
I often get excited by some discovery sounding a lot older than it actually is, for reasons like this.