@singingwolfboy Renamed string variable name. Regarding robust check: re.match is much slower that comparison, also, we are checking result of standard library function, which is well documented
:link: http://docs.python.org/2/library/datetime.html#datetime.timedelta
```str(t)	Returns a string in the form [D day[s], ][H]H:MM:SS[.UUUUUU], where D is negative for negative t. (5)```