XCalendar:
    | "gregorian"
    | "chinese"
    | "coptic"
    | "discworld"
    | "ethiopian"
    | "hebrew"
    | "islamic"
    | "julian"
    | "mayan"
    | "nanakshahi"
    | "nepali"
    | "persian"
    | "jalali"
    | "taiwan"
    | "thai"
    | "ummalqura"