'Convert a year/month/day tuple of this calendar into
a Julian day number (matching jQuery calendars algorithm)
@param year: the year number
@param month: the month number
@param day: the day-of-month number'

@classmethod
def to_jd(cls, year, month, day):

    if (year >= 0):
        ep_base = (year - 474)
    else:
        ep_base = (year - 473)
    ep_year = (474 + (ep_base % 2820))
    if (month <= 7):
        mm = ((month - 1) * 31)
    else:
        mm = (((month - 1) * 30) + 6)
    result = ((((((day + mm) + math.floor((((ep_year * 682) - 110) / 2816))) + ((ep_year - 1) * 365)) + (math.floor((ep_base / 2820)) * 1029983)) + cls.JDEPOCH) - 1)
    return result
