Entering Dates as strtings
The main problem with entering dates as string values is the potential for misinterpretation by a program or section of a calcuation. To aviod this it is suggested that you use the DATE() function when entering dates in to calcuations. The DATE() specified the year , month, day to be enterted and then returns a serial number that uniquly identifies the date as a series of digits.

Ambiguities include:

US vs Eropean date conventions eg. In the US 02/05/2007 means Febuary 5th 2007 where as in Europe it would be interpreted as May 2nd 2007. Excel can for dates using both methods but be sure you have selected the correct one. otherwise Excel will misinterpret dastes entered as text strings.

Year 2000 issues eg. when sriting a date such as 06/05/28 excel will interpret this as 1928 not 2028 unless you set the default formatting to recognize 2-digit years as representing a year in the 21st century.