[tz] Leap year bugs

[Clive D.W. Feather]

Brian Inglis said:
> > My understanding (and, no, I don't have references) is that all of Europe
> > had 29th February (whether the leap day is VI Kal.Mar. or 29th February is
> > a notational matter and not relevant) in the same Februaries, so that the
> > 29th February would be in 1743 and 1747 in England but in 1744 and 1748 in
> > Scotland *but it's the same February*.
> 
> So the new year celebrated in that 12 month period was used to determine when
> leap years occurred.

That would appear to be the case, yes.

> The leap day was apparently still considered effectively to be added after ante
> diem sexto Kalendis Martis (February 24), giving ante diem bis sextus Kalendis
> Martis, second sixth (inclusive count) day before March 1, which is why that is
> not mentioned in the bull.
> 
> It was probably not until the common use of Hindu-Arabic numerals replacing
> Roman numerals in calendars (apparently undocumented so far) when February
> having 29 days gave rise to the belief that the added day was the 29th.

Agreed. In my text quoted above I should perhaps have written "... had a
29-day February ...".

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Clive D.W. Feather          | If you lie to the compiler,
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