Parses strings expressing the day and/or time, such as 12/4/61 4:03:15.
The date part should look like this: [M]M/[D]D[/YY] and the time part should
look like this: [H]H(:|.)MM[(:|.)[SS]][AM|PM].
The time part must have a colon; the
seconds are optional. If the time part is missing, it defaults to midnight.
Six values are returned, suitable for giving to `encode-universal-time.' If the
optional argument is true, this encoding is done for you, and a universal time
is returned. If 'future?' and no date is given the returned time is guaranteed to be
in the future.