Extended ranges required for dates and date-times

David Jarvie lists at astrojar.org.uk
Thu Feb 9 21:57:15 GMT 2006

On Thursday 9 February 2006 18:40, Jason Harris wrote:
>One issue that has not been mentioned: what is to be done for calendar 
>dates prior to 1752, for which identifying a particular calendar date 
>becomes ambiguous (due to different calendar systems in use prior to 
>1752)?  We handle this very simply in ExtDate: we totally ignore it, and 
>simply extrapolate the modern Gregorian calendar backward.  Thus ancient 
>dates in ExtDate are not *historically* accurate, but they are more 
>*seasonally* accurate (which was more important for us in KStars).

This was what made me doubt the desirability of using ExtDate in KDateTime 
originally. However, it has become apparent to me since then that there are a 
number of applications which use the Gregorian calendar extended backwards to 
before it came into actual use - and not just astronomical applications.

Another consideration is that it was originally introduced in 1582 (long 
before QDate's 1752 which is when the UK adopted it), and was adopted 
gradually in different countries. In Europe, Greece did not adopt it until the 
20th century. So it is only in very recent times that it has been universally 
used, and reliably corresponds to historical dates throughout the world.

David Jarvie.
KAlarm author & maintainer.

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