2.5.5.1 says: "A month consists of a specific proleptic Gregorian date"; 2.5.5.2 says likewise: "A date consists of a specific proleptic Gregorian date". Similar references are made in 2.5.5.5, 2.5.5.7, and 2.5.5.8.

The word "proleptic" is used here to mean "use the Gregorian calendar regardless of whether it was actually in effect at the time you're talking about." However, its actual meaning is a date that *is* before the introduction of the calendar, not that it merely *could* be before then. (If one wanted to interpret the specification strictly, you could say that this makes it an error to mark up dates after 1582; this would be rather silly, though.)

I suggest fixing this by changing both to read "... consists of a specific Gregorian date, using the calendar proleptically before its introduction, ..."