Defined in header
leap represents the date and time of a leap second insertion.
Users cannot construct
leap objects except by copying from existing
leap objects. The library implementation creates
leap objects when it initializes the time zone database and provides const access to these objects.
leap has a defaulted copy constructor and a defaulted copy assignment operator.
 Member functions
| obtains the time of leap second insertion |
(public member function)
 Nonmember functions
| compares two |