Excel2007 找不到datedif() 函数的原因

　今天在学Excel2007常用公式时，发现一个函数datedif(),在帮助里面找不到相关的信息，但是又可以正常的使用。很奇怪，在网上搜索“Excel 2007datedif”，找到了原因。


The DATEDIF worksheet function
The DATEDIF function calculates the difference between two dates, and expresses the result in terms of months, days, or years.

If you have Excel version 5.0 or later, you can make use of the handy DATEDIF function in your formulas. But if you want to read about this function in the online help, you must have Excel 2000. For some reason, the function was never documented until Excel 2000. And the documentation was removed from Excel 2002.

The DATEDIF function has its origins in Lotus 1-2-3. Apparently, Microsoft included it in Excel for compatibility purposes. Why is it not documented? Who knows? But it's likely that lawyers are involved.