|  | 
        In the table below, X denotes
        a time traits class for time type Time,
        t, t1,
        and t2 denote values of type
        Time, and d
        denotes a value of type X::duration_type.
      
Table 33. TimeTraits requirements
| expression | return type | 
                  assertion/note | 
|---|---|---|
| 
                   | 
                   | 
                  Represents an absolute time. Must support default construction,
                  and meet the requirements for  | 
| 
                   | 
                  Represents the difference between two absolute times. Must support
                  default construction, and meet the requirements for  | |
| 
                   | 
                   | Returns the current time. | 
| 
                   | 
                   | 
                  Returns a new absolute time resulting from adding the duration
                   | 
| 
                   | 
                   | 
                  Returns the duration resulting from subtracting  | 
| 
                   | 
                   | 
                  Returns whether  | 
| 
                   | 
                   | 
                  Returns the  |