<=> — Compares intervals
baseintervalObj.<=>(interval)
#<=> compares baseintervalObj with interval and returns -1 if baseintervalObj is less than interval, 0 if they are equal or 1 if interval is less than baseintervalObj. interval must be the same interval type as baseintervalObj. This is because of a limitation of the OCI: it will only subtract intervals of the same type.