The Compare Midpoint Times routine compares two binary timestamps
    and returns a flag indicating that the first timestamp is greater
    than, less than, or equal to the second timestamp. Inaccuracy
    information is ignored for this comparison; the input values
    are, therefore, equivalent to the midpoints of the time intervals
    described by the input binary timestamps.

    The input binary timestamps express two absolute or two relative
    times. Do not compare relative binary timestamps and binary
    timestamps. If you do, no meaningful results and no errors are
    returned.

    The following routine does a lexical ordering on the time
    interval midpoints.

    utc1 is utc_lessThan utc2 iff
            utc1.time < utc2.time

    utc1 is utc_greaterThan utc2 iff
            utc1.time > utc2.time

    utc1 is utc_equalTo utc2 iff
            utc1.time == utc2.time