2.1.1101 Part 4 Section 3.17.7.348, YEARFRAC
a. The standard does not describe day and month adjustments for the argument basis.
In Excel, the basis argument specifies the truncated integer type of day count basis to use, as follows:
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Value |
Day Count Basis |
|---|---|
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US (NASD) 30/360.Assumes that each month has 30 days and the total number of days in the year is 360 by making the following adjustments: • If the date is 28 or 29 February, it is adjusted to 30 February. • For months with 31 days, all dates with a day value of 31 are changed to day 30, including situations where the first date is 28 or 29 February. |
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Actual/actual. The actual number of days between the two dates are counted. If the date range includes the date 29 February, the year is 366 days; otherwise it is 365 days. |
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Actual/360. Similar to Basis 1, but only has 360 days per year. |
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Actual/365. Similar to Basis 1, but always has 365 days per year. |
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European 30/360.The European method for adjusting day counts. Assumes that each month has 30 days and the total number of days in the year is 360 by making the following adjustments: If the date is 28 or 29 February, it is adjusted to 30 February. For months with 31 days, all dates with a day value of 31 are changed to day 30, including situations where the first date is 28 or 29 February. |
b. The standard lists day-count-basis as one of the function's arguments.
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In Excel, the function does not take a day-count-basis argument.
c. The standard does not specify any restrictions on arguments start-date or end-date.
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Office returns #NUM! if arguments start-date or end-date is out of range for the current date base value.
d. The standard does not describe year length adjustments when argument basis is Actual/actual.
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In Office, if the argument basis is Actual/actual, the year length used is the average length of the years that the range crosses, regardless of where arguments start-date and end-date fall in their respective years.