We have our own preferable ways to write the date format. Most of the great software honor this and allow users to configure the pattern of a date.
If you are creating a PDF form using Adobe LiveCycle Designer ES3, having a date format of your choice is a walk in the park. LC Designer offers many pre-defined formats for the purpose, and also lets you define your own custom formats using the building blocks, such as MM for month, YY for 2-digit year, and YYYY for 4-digit value of the year. Watch the video to see how do so.
For more information see the following links:
A complete list of Adobe LiveCycle Designer ES3 documentation.
Detailed information about date patterns in Designer Help.
Check out the Designer FAQ for more Q&A.