Your task is to open a file containing a list of dates in
various formats, read each date, determine if it is a valid format
and print it in **ISO 8601 format**(YYYY/MM/DD) to console. The
list will be terminated by a `-1`.
There are **two** valid formats:
- plain-language format: <Month> <Day>, <Year>
where Day and Year are valid integers. ex. `March 3, 1990`.
- reversed ISO format, `DD/MM/YYYY` (Note that we aren't concerned
with the precise ordering of month...