0 Indicates success.
-1 Indicates failure; errno is set to the
following value:
o EINVAL - The clock_id argument does not
specify a known clock, or the tp argument
is outside the range for the given clock_id
or specifies a nanosecond value less than 0
or greater than or equal to 1 billion.
o EPERM - The requesting process does not
have the appropriate privilege to set the
specified clock.