The system realtime clock is guaranteed to be monotonically
increasing at all times. As such, all calls to these functions
are guaranteed to return a system time greater than or equal to
the system time returned in any previous calls.
The guarantee to return a result "greater than or equal to" the previous
result is a property of a "monotonically non-decreasing" function. A
"monotonically increasing" function would guarantee a results that is
strictly greater than any previous results.
So, which is correct here? :)