Days-until calculator (r/dailyprogrammer Easy #2)

daysuntil.py

#!/usr/bin/env python

import datetime, sys

today = datetime.date.today()
month = today.month
year = today.year

if len(sys.argv) == 2:
    day = int(sys.argv[1])
elif len(sys.argv) == 3:
    day = int(sys.argv[1])
    month = int(sys.argv[2])
elif len(sys.argv) == 4:
    day = int(sys.argv[1])
    month = int(sys.argv[2])
    year = int(sys.argv[3])
else:
    from os.path import basename
    print "Usage: {} day [month [year]]".format(basename(__file__))
    sys.exit(1)

try:
    then = datetime.date(year, month, day)
    delta = then - today
    preposition = "until" if delta.days >= 0 else "since"
    print abs(delta.days), "days", preposition, then,
    sys.exit(0)
except ValueError:
    print "Not a valid date."
    sys.exit(1)

usage.sh-session

$ ./daysuntil 15
7 days until 2014-08-15
$ ./daysuntil 8 3
153 days since 2014-03-08
$ ./daysuntil 24 8
16 days until 2014-08-24
$ ./daysuntil 1 6 2016
663 days until 2016-06-01
$ ./daysuntil
Usage: daysuntil.py day [month [year]]
$ ./daysuntil 1 6 201 6
Usage: daysuntil.py day [month [year]]