#!/bin/env python3

from sys import argv, exit
from time import ctime

ddic = {}
ddic['Jan'] = '01'
ddic['Feb'] = '02'
ddic['Mar'] = '03'
ddic['Apr'] = '04'
ddic['May'] = '05'
ddic['Jun'] = '06'
ddic['Jul'] = '07'
ddic['Aug'] = '08'
ddic['Sep'] = '09'
ddic['Oct'] = '10'
ddic['Nov'] = '11'
ddic['Dec'] = '12'

# Based on John Ball's DAZE.F

def mjd(year, doy):
	NYR = int(year)
	NYRD = int(doy)
	# L2 IS -1 IF LEAP YEAR, -2 IF NOT. 
	L2 = NYR//4-(NYR+7)//4-NYR//100+(NYR+99)//100+NYR//400-(NYR+399)//400
	MO = (12*NYRD+356+(NYRD+322)//367*(6-12*L2))//367
	NDA = NYRD-(367*MO-362)//12-(MO+9)//12*L2
	NYR1 = NYR-1
	MJD = NYRD-678576+365*NYR1+NYR1//4-NYR1//100+NYR1//400
	return MJD, MO, NDA

def doy(year, mo, day):
	NYR = int(year)
	L2 = NYR//4-(NYR+7)//4-NYR//100+(NYR+99)//100+NYR//400-(NYR+399)//400
	monstart1 = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334]
	monstart2 = [0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335]
	if L2 == -1:
		return day + monstart2[mo-1]
	else:
		return day + monstart1[mo-1]

def parsetime(ts):
	parts = ts.split(':')
	factor = 1.0/24.0
	t = 0.0
	for p in parts:
		t = t + factor*float(p)
		factor = factor/60.0
	return t

def parseday(ds):
	parts = ds.split('/')
	if len(parts) == 1:
		year = float(parts[0])
		NYR = int(year)
		fy = year - NYR
		L2 = NYR//4-(NYR+7)//4-NYR//100+(NYR+99)//100+NYR//400-(NYR+399)//400
		if L2 == -1:
			return NYR, int(fy*366.0)+1
		else:
			return NYR, int(fy*365.0)+1
	elif len(parts) == 2:
		return int(parts[0]), int(parts[1])
	elif len(parts) == 3:
		return int(parts[0]), doy(int(parts[0]), int(parts[1]), int(parts[2]))
	else:
		exit(0)

if len(argv) < 2:
	print('Usage(0) : %s  --> return help info and todays mjd' % argv[0])
	print('Usage(1) : %s year/month/day [hour[:min[:sec]]]' % argv[0])
	print('Usage(2) : %s year/d.o.y. [hour[:min[:sec]]]' % argv[0])
	print('\nMJD now is given by:')
	
if len(argv) < 2:
	s = ctime().strip().split()
	ts = s[3]
	day = s[4]+'/'+ddic[s[1]]+'/'+s[2]
elif len(argv) < 3:
	ts = '00:00:00'
	day = argv[1]
else:
	ts = argv[2]
	day = argv[1]

time = parsetime(ts)
year, doy = parseday(day)

imjd, mo, da = mjd(year, doy)

mjd = float(imjd) + time
jd = mjd + 2400000.5

print('%d/%d/%d [%d] %s -> MJD %f  JD %f' % (year, mo, da, doy, ts, mjd, jd))