Microsoft KB Archive/73210

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Days360 Calculates as Designed in Excel

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The information in this article applies to:


 * Microsoft Excel for Windows, versions 3.x, 4.x, 5.0
 * Microsoft Excel for Windows, version 7.0
 * Microsoft Excel for the Macintosh, versions 3.x, 4.x, 5.0

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SUMMARY
Microsoft Excel has a DAYS360 function, which is designed to calculate the number of days between two specified dates based on a 360-day year, instead of the normal 365-day year.

MORE INFORMATION
DAYS360 is based on twelve 30-day months and treats each month as such. This is useful to help compute payments if your accounting system is based on twelve 30-day months. So, when DAYS360 calculates the number of days between 2/28/91 and 3/1/91 as 3, this is correct. DAYS360 assumes that February has 30 days, not 28 (or 29 in a leap year). Likewise, DAYS360 treats the dates &quot;1/30/91&quot; and &quot;1/31/91&quot; identically. &quot;1/31/91&quot; is converted to &quot;1/30/91&quot;.

DAYS360 does conform to the standards established by the NASD (National Association of Security Dealers), and the SIA standards which specify that:


 * if the start date is the 31st of a month, it is equal to the 30th of the same month
 * if the end date is the 31st of a month, it is equal to the 1st of the next month

except when the start date is the 30th of a month.

The European method of this function is more simple. The 31st of a month is always equal to the 30th of the same month.

DAYS360 calculates as designed and as described in the &quot;Function Reference&quot;.