Modifying Action Diagrams › Understanding Built-In Functions › *DURATION Rules and Examples

*DURATION Rules and Examples

*DURATION performs the following operation:

End date - Start date = Duration

The *DURATION function result is often not as obvious and easily predictable as the *DATE INCREMENT result. For example, what is the duration expressed in *MONTHS between Start date (December 31, 1995) and End date (February 29, 1996)? The function returns two months even though three months are involved in the calculation. This is another example of the Everyday calendar’s approximation.

The remainder of this section gives examples of specific assumptions CA 2E makes to adjust results to common sense standards and to produce consistent results.

• The *DURATION function counts a month if the number of covered days is greater than or equal to the number of days in the End date month. A Duration month is defined as the number of days in the End date month. Note that the first day of a duration interval is never counted.

• The *DURATION function counts a year if any twelve consecutive months are covered. This is the definition of a Duration year. Note that the first day of a duration interval is never counted.

• For the *YYMMDD duration type, DD represents the number of days not included in either the Duration year (YY) nor the Duration month (MM).

Following are the steps used to produce this result.

1. Calculate years. From within the range of dates, identify any whole years consisting of 12 consecutive whole months. For example, December 1, 1995 to November 30, 1996 = 1 year.
2. Calculate months. From within the remaining dates, identify any whole months; in this example, December 1996 + January 1997 + February 1997 = 3 months.
3. Calculate days. All that remains from the original date range are parts of the first and last months in the range; namely, November 12, 1995 to November 30, 1995 (18 days) and March 1, 1997 to March 23, 1997 (23 days). The total number of remainder days is 41 (18 + 23 = 41). Since 41 days is greater than the Duration month of 31, add one month to the total number of months (3 + 1 = 4 months).

   Recall that the DD portion of the *YYMMDD duration type represents the number of days not included in either the Duration year (YY) or the Duration month (MM). In other words, Remainder days (DD) – Duration month = 10 days (41 – 31 = 10).

The final result in *YYMMDD format is 10410.

• The *DURATION function calculates one month if both the Start and End dates represent the same day in contiguous months.

Application of this rule sometimes causes different, but close, Start and End dates to return the same duration.

• The *DURATION function calculates one year if both Start and End dates represent the same day and month in contiguous years.

Application of this rule sometimes causes different, but close, Start and End dates to return the same duration.