Issued: January 28, 2011
Impact: All US GAAP


In a number of cases, filers are defining number values (e.g., data types derived from integer or decimal) that represent days months or years as an integer data type. For example, a company created an extension element called NoticePeriodForIncreaseInFacilityAmount with an integer data type.  The value in the instance was 20.  The issuer should have used the data type durationItemType for this extension and entered the value P20D, as defined in ISO 8601 in the instance.  The durationtemType is an equivalent of the XML schema duration item type and should be used in the same manner. See In the case where a duration needs to be defined that is modified by text, then durationStringItemType should be used. For example, “From 6 months to 5 years” uses text to modify or qualify that duration.


When creating an extension element that represents an actual duration of time, such as days, months and years, the data type durationItemType should be used. When creating an element that represents a duration that could have textual modifiers, then use the data type durationStringItemType.  If the actual value of a durationStringItemType is a specific duration, then the restrictions that apply to the durationItemType should be followed (see figure below). Refer to item 6.6.37 in the Edgar Filer Manual.

The formatting options for durationItemType are as follows:

Period Code Example
Period Indicator P Indicates a Period
Year Y P1Y is one year
Months M P1M is one month
Days D P6D is 6 days
Time Indicator T Separates a time from a date.
Hours H T10H is 10 hours
Minutes M T30M is 30 minutes
Seconds S T30S is 30 seconds

For example, P2Y3M2DT10H30M5S is equal to a period of 2 Years, 3 Months, 2 days, 10 hours, 30 minutes, and 5 seconds.
The date string item type follows a similar logic to the duration string item type and is used for elements for which the fact values are usually a specific date, but may be accompanied by text that modifies or qualifies the date.

If the date is known and specific, then it must appear in the form – CCYY-MM-DD. Otherwise, durationString values such as “After 2007” or “before March 31, 2009” are acceptable.

For example, “Tuesday, October 19, 2010” violates this rule and must be expressed as 2010-10-19.