You can only compare UNTIL_CHANGED to the ending bound of a Period value with an element type of DATE or TIMESTAMP WITH TIME ZONE. Therefore, the result type of the END function must be DATE or TIMESTAMP WITH TIME ZONE. For information about the END function, see END.
In comparisons, the precision of the UNTIL_CHANGED value is truncated to the precision of the ending bound value being compared. That is, the number of digits after the decimal point for UNTIL_CHANGED depends upon the precision of the ending bound to which it is compared. The time zone is omitted if the ending bound value has no time zone.
If the ending bound value is NULL, IS [NOT] UNTIL_CHANGED returns UNKNOWN.
You cannot use IS [NOT] UNTIL_CHANGED on the ending bound of a system-time or temporal table columns.