parseTimeOfDay

Parse HH:mm:ss or HH:mm:ss.nnnnnnnnn text into a time of day, returning null when text is not one of those.

Returns null when the clock part does not hold three :-separated fields, a field is empty or holds anything but digits, the hour is outside 0..23, a minute or second is outside 0..59, or the fractional part is outside 0..999999999. Field widths are not enforced, so "9:30:00" reads as 09:30:00. Any Unicode decimal digit is accepted, so Devanagari input reads the same as Latin.

The fractional part counts nanoseconds, so ".7" is seven nanoseconds, not seven tenths of a second.