Calendar

A module to convert dates to different calendars

Download Calendar v0.10 (22-Sep-2003) [64k Spark archive]

What is Calendar

This module was designed to convert dates from one calendar to another, for example between Gregorian and Julian. As a side-effect it will also let jou do calculations on dates within the same calendar. E.g. you can find out how many days there are between 1961-APR-06 and 1988-Aug-22. You can read a preliminary HTML version of the manual [23k] for more details.

Features

Features of version 0.10

This is still a preliminary version, which only supports the Julian and the Gregorian calender, and the only SWIs available are Calendar_DateToGDay and Calendar_GDayToDate.
Important change: In contrast to what the manual said, the internal day number has changed in this release of Calendar. Previously 1-Jan-0001 in the Gregorian calendar is taken as day 1. I called this the Gregorian Day Number. Now this has changed to the already widespread Julian Day Number as used in astronomy.
The reasons for this change is to:
1. Reduce the chance of negative day numbers.
2. Connect to a well established existing system of counting the days.
A little library of C veneers has been added, called CalLib.
A demo program which uses the C veneers is included in the package. It shows a simple dialogue window with fields for day, month, year and others. Each field can be changed and the other fields follow.

Future features

Support the Hebrew, Islamic and French Revolutionary calendars.
More SWIs, such as JDayToWeek, WeekToJDay and CheckDate will be added.
An effort will be made to let the conversions support out-of-range month numbers, such as zero or less, or larger than the number of months in a year. This is most easely done for calendars that have a fixed number of months in the year.
For the moment no calculations can be made for years less than 1. It would be nice to be able to work with, e.g. 'BC' dates.
A SWI may be added to calculate variable religious days, like Easter.

Giving the module away

You are strongly advised to distribute the Calendar module and the accompanying files and to give it to any RISC OS machine owners you know. This module and the accompanying files are FREEWARE, i.e. it may be copied freely, provided that no part of it is deleted or changed and that it is not sold for profit.

For questions, remarks, suggestions, comments etc. see the contacts page

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File identification:

$Id: calendar.html 1.7 2006/10/04 09:58:51 erikgrnh Exp $