软件包: libdate-jd-perl (0.006-1)

conversion between flavours of Julian Date

For date and time calculations it is convenient to represent dates by a simple linear count of days, rather than in a particular calendar. This is such a good idea that it has been invented several times. If there were a single such linear count then it would be the obvious data interchange format between calendar modules. With several versions, calendar modules can use such sensible data formats and still have interoperability problems. Date::JD tackles that problem, by performing conversions between different flavours of day count. These day count systems are generically known as "Julian Dates", after the most venerable of them.

Among Julian Date systems there are also some non-trivial differences of concept. There are systems that count only complete days, and those that count fractional days also. There are some that are fixed to Universal Time (time on the prime meridian), and others that are interpreted according to a timezone. Some consider the day to start at noon and others at midnight, which is semantically significant for the complete-day counts. The functions of this module appropriately handle the semantics of all the non-trivial conversions.