comma to delimit fractional seconds

I'm new at this.

I looked at the TODO list and saw the issue of using comma to delimit 
fractional seconds.

I looked at the parser stuff and I think I have at least a start on the 
issue.

Is there anything more to it than allowing HH:MM:SS,####### as well as 
HH:MM:SS.##### ?

Is it OK if it works that way in all timestamps, not just 
ISO-8601-compliant cases?


Chris Howard