Value,Description,Reference
second,The unit of the element content is seconds.,[RFC7970]
minute,The unit of the element content is minutes.,[RFC7970]
hour,The unit of the element content is hours.,[RFC7970]
day,The unit of the element content is days.,[RFC7970]
month,The unit of the element content is months.,[RFC7970]
quarter,The unit of the element content is quarters.,[RFC7970]
year,The unit of the element content is years.,[RFC7970]
ext-value,"A value used to indicate that this attribute is
        extended and the actual value is provided using the
        corresponding ext-* attribute.  See Section 5.1.1 of [RFC7970].",[RFC7970]