Signed fractions of a second at nanosecond resolution of the span
of time. Durations less than one second are represented with a 0
seconds field and a positive or negative nanos field. For durations
of one second or more, a non-zero value for the nanos field must be
of the same sign as the seconds field. Must be from -999,999,999
to +999,999,999 inclusive.
Signed seconds of the span of time. Must be from -315,576,000,000
to +315,576,000,000 inclusive. Note: these bounds are computed from:
60 sec/min * 60 min/hr * 24 hr/day * 365.25 days/year * 10000 years
