The specs say that hours must be at least two digits, meaning more
than 99 hours must be supported.
The specs also contain suggested ways for parsers to be a bit more
lenient with certain aspects of the timestamps:
1. Spaces & tabs at the start of the line are OK.
2. Arbitrary number of space & tabs around the arrow are OK.
3. The hours component can also be one digit only.
Fixes & implements #3139.
