cpp/chrono/hour fun

These functions aid in translating between a 12-hour format time of day, and a 24-hour format time of day.

@1@ Detects whether the 24-hour format time is a.m. (ante meridiem, before midday).

@2@ Detects whether the 24-hour format time is p.m. (post meridiem, after midday).

@3@ Returns the 12-hour equivalent of a 24-hour format time.

@4@ Returns the 24-hour equivalent of a 12-hour format time, where determines whether the time is p.m.

Return value
@1@ . @2@ . @3@ If is in range, returns the 12-hour equivalent in range. Otherwise, the return value is unspecified. @4@ If is in range, returns the 24-hour equivalent in range  if  is , or in range  otherwise. Otherwise, the return value is unspecified.