Date Field Format

• Excel assigns sequential serial numbers to each date, such as 40415 for August 25, 2010, and compares dates by calculating differences between them. To differentiate hours, minutes and seconds in a day, Excel adds decimal places in the serial number. Excel can consider a date field based on a static date or by a dynamic formula.
  
  

Significance

• Comparing date fields increases the productivity of applications such as by analyzing time series data, error checking independent streams of data and summarizing data into longer time periods. Problems that arise in date field comparisons can be time-consuming to resolve, especially with large dynamic data sets.
  
  

Considerations

• Users can see two display date fields that look identical but are different, or they may find that some date comparisons change over time. Often, seeing the date displayed does not demystify. When comparing dates fields, know whether the fields are both static or dynamic by checking the formula bar. Consider the calendar systems of other spreadsheet programs when dealing with imported date fields, and run independent test comparisons to ensure that the date fields are the same.