Many different #calendars are in use. We are approaching the year 2014 of the "
common era". This year is however not in use everywhere. This is for instance reflected in
the "concept cloud" for Jordan. You will find a reference to
۱۳۲۸ or 1328 HS. When you see a date with the addition of HS, it is a date in a solar calendar that starts with the hijri or
Muhammad's migration to Medina (622 CE).
This
solar hijiri calendar is quite different from the "common era calendar". The first six months have 31 days, the next five have 30 days, and the last month has 29 days in usual years but 30 days in leap years. It begins on the
vernal equinox as determined by astronomical calculations for the
Iran Standard Time meridian (52.5°E or GMT+3.5h). This determination of starting moment is more accurate than the Gregorian calendar for predicting the date of the vernal equinox, because it uses astronomical calculation rather than mathematical rules.
At this time you can only enter "common era" based dates in
Wikidata. This is sad because we do lose precision as a result. When something occurred in a the year 1328 HS for instance, three months are in another "common era" year. When you look for illustrations in
Commons for the solar hijri calendar, you find them in the same category as the moon based or common hijiri calendar.
In Wikidata, a bot has run to add Latin labels for Dutch and English for the items for the years of this calendar. When you then check "
2013 CE", you find its labels are problematic. Check out the statements for "
year", it presumes that a year is a "common era" year. It does not define itself as being a year in what calendar. Obviously a year like "1328" is not well defined, as it could be in several calendars.
Thanks,
GerardM
