Property:Date-calendar

String
 * Allowed values:
 * allows value::Gregorian (nearly all dates since 1752, excepting some in Slavic/ Eastern Orthodox countries)
 * allows value::Julian (everything before 1582, and some before 1752 in english speaking countries)
 * allows value::Roman republican
 * allows value::Hebrew
 * allows value::Islamic
 * allows value::Chinese