XL2000: Method to Determine Whether a Year Is a Leap Year

ID: Q214019

The information in this article applies to:

Microsoft Excel 2000

SUMMARY

This article contains information that explains how to determine whether the year in a date used in a Microsoft Excel document is a leap year.

MORE INFORMATION

The date system used by Excel is based on the Gregorian calendar, first established in 1582 by Pope Gregory XIII. This calendar was designed to correct the errors introduced by the less accurate Julian calendar.

In the Gregorian calendar, a normal year consists of 365 days. Because the actual length of a sidereal year (the time required for the Earth to revolve once about the Sun) is actually 365.25635 days, a "leap year" of 366 days is used once every four years to eliminate the error caused by three normal (but short) years. Any year that is evenly divisible by 4 is a leap year: for example, 1988, 1992, and 1996 are leap years.

However, there is still a small error that must be accounted for. To eliminate this error, the Gregorian calendar stipulates that a year that is evenly divisible by 100 (for example, 1900) is a leap year only if it is also evenly divisible by 400.

For this reason, the following years ARE NOT leap years

1700, 1800, 1900, 2100, 2200, 2300, 2500, 2600

because they are evenly divisible by 100 but NOT by 400.

The following years ARE leap years

1600, 2000, 2400

because they are evenly divisible by both 100 and 400.

Because earlier versions of Microsoft Excel handle only years from 1900 to 2078, only the year 1900 is subject to the 100/400 exclusion rule of leap years in Microsoft Excel. However, in order to be compatible with other programs, Microsoft Excel treats the year 1900 as a leap year.

For additional information, please see the following article in the Microsoft Knowledge Base:

Q214058 XL2000: Days of the Week Before March 1, 1900 Are Incorrect

To Determine If a Year Is a Leap Year

To determine if a year is a leap year, follow these steps:

If the year is evenly divisible by 4, go to step 2. Otherwise, go to step 5.

If the year is evenly divisible by 100, go to step 3. Otherwise, go to step 4.

If the year is evenly divisible by 400, go to step 4. Otherwise, go to step 5.

The year is a leap year (it has 366 days).

The year is not a leap year (it has 365 days).

Formula to Determine If a Year Is a Leap Year

The following formula will determine whether the year number entered into a cell (in this example, cell A1) is a leap year:

=IF(OR(MOD(A1,400)=0,AND(MOD(A1,4)=0,MOD(A1,100)<>0)),"Leap Year", "NOT a Leap Year")


   If the value in cell A1 is this        The formula returns
   ----------------------------------------------------------
   1992                                   Leap Year
   2000                                   Leap Year
   1900                                   NOT a Leap Year

REFERENCES

For more information about how Microsoft products are affected by year 2000 (Y2K) issues, please see the following Microsoft World Wide Web site:

http://www.microsoft.com/y2k/

Additional query words: XL2000 y2k years leapyear 365 366

Keywords : kb2000 xlformula
Version : WINDOWS:2000
Platform : WINDOWS
Issue type : kbhowto