[WIP] Create calendar definition rules

[tukusejssirs]

Related #91 #26

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This issue should serve to make decision(s) how the celebrations (be it event celebrations or saint celebrations) in calendars should be defined in v2.0.0.

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My suggestions:

• the celebrations should the following meta-properties/metadata:
  • startDate – when the celebration was included into the calendar:
    • for celebrations that are in the calendar since the Second Vatican Council / Mysterii Paschalis, that is since the establishment of the new, revised General Roman Calendar, there should be the date when this new Calendar was put into effect, i.e. 1 January 1970 (src);
    • for other celebrations, this should be the date when the particular celebration became effective;
    • when a celebration was changed somehow (like moving it to different date or changing its celebration rank), the previous celebration should be ‘finished’ (i.e. the endDate should be defined) and a new definition should be defined;
    • when not defined, it will be implicitly considered that it was defined when the particular calendar revision (like Cal1962 or Cal1969) came to effect; this, however, should be used only when one is not sure (i.e. when one is sure they know the startDate, they must define this in the celebration definition);
    • when the exact date is unknown, one may define only MM/YYYY or even YYYY;
  • endDate – the date since when a particular celebration is not celebrated in the particular calendar:
    • when not defined, it is implicitly considered that the endDate is the date when the particular calendar revision has been ‘discontinued’ (i.e. when they are stopped being used by the Church);
    • when the exact date is unknown, one may define only MM/YYYY or even YYYY;
• add calendar (like Cal1962 or Cal1969) definitions:
  • these definitions would defined the calendar metadata, like:
    • startDate – when it became effective;
    • endDate – when it stopped being effective;
    • issuer (might be renamed) – which pope ‘promulgated’/revised the particular calendar;

Notes:

• the startDate and endDate will be useful for histcal (#23);
• celebrations order:
  • celebrations with fixed date should be ordered in calendar year order (from 1 Jan to 31 Dec);
  • celebrations with variable date should be listed at the end of the calender file in alphabetical order by key name;