compares two date-and-time objects
| std::less | compares two objects in an object specific way |
| std_types::date_and_time/std::equal | compares two date-and-time objects for equality |
| std_types::date_and_time/std::plus | adds an arbitrary time delta to a date-and-time object |
| std_types::date_and_time/std::minus | subtracts a time delta or another date-and-time object from a date-and-time object |