Spotify Puzzles

Best Before Puzzle

http://www.spotify.com/us/jobs/tech/best-before/

Correct

$ python bestbefore.py
2001/01/03
2001-01-03

$ python bestbefore.py
2001/03/01
2001-01-03

$ python bestbefore.py
03/01/01
2001-01-03

$ python bestbefore.py
03/01/112
2112-01-03

$ python bestbefore.py
12/11/10
2010-11-12

$ python bestbefore.py
10/11/12
2010-11-12

$ python bestbefore.py
11/12/10
2010-11-12

$ python bestbefore.py
11/30/999
2999-11-30

$ python bestbefore.py
11/32/1
2032-01-11

Errors

$ python bestbefore.py
11/31/2001
11/31/2001 is illegal

$ python bestbefore.py
11/31/
11/31/ is illegal