jalali_ordinal.py

jalali_ordinal.py

'''
jd - ordinal = 1721425
jd = ordinal + 1721425
ordinal = jd - 1721425

>>> date=(2015, 12, 19) ; gregorian.to_jd(*date) - datetime(*date).toordinal()
1721425

'''

from bisect import bisect_left

monthLen = (31, 31, 31, 31, 31, 31, 30, 30, 30, 30, 30, 30)

monthLenSum = [0]
for i in range(12):
    monthLenSum.append(monthLenSum[-1] + monthLen[i])

def getMonthDayFromYdays(yday):
    month = bisect_left(monthLenSum, yday)
    day = yday - monthLenSum[month - 1]
    return month, day

def jalali_to_ordinal(year, month, day):
    y2 = year - 979
    jdays = 365*y2 + y2//33 * 8 + (y2%33+3)//4 + monthLenSum[month-1] + (day-1)
    return jdays + 584102

def ordinal_to_jalali(ordinal):
    jdays = int(ordinal - 584102)
    ## -(1600*365 + 1600//4 - 1600//100 + 1600//400) + 365    -79 +1== -584101
    #print('jdays =',jdays)
    j_np = jdays // 12053
    jdays %= 12053
    year = 979 + 33*j_np + 4*(jdays//1461)
    jdays %= 1461
    if jdays >= 366:
        year += (jdays-1) // 365
        jdays = (jdays-1) % 365
    yday = jdays+1
    month, day = getMonthDayFromYdays(yday)
    return year, month, day


if __name__=='__main__':
    from datetime import datetime
    now_dt = datetime.now()
    today_ordinal = now_dt.toordinal()
    for ordinal in range(today_ordinal, today_ordinal-100, -1):
        j_date = ordinal_to_jalali(ordinal)
        assert jalali_to_ordinal(*j_date) == ordinal
        j_str = '%.4d-%.2d-%.2d'%j_date
        g_str = datetime.fromordinal(ordinal).strftime('%Y-%m-%d')
        print '%s   %s'%(g_str, j_str)