The day, month, year and century, or any combination of these elements, of an event.

This is the e-Government Interoperability Framework (e-GIF) standard that should be used for all new and developing systems and for XML messages.

Concatenated date time elements are in use and are derived from the e-GIF standards for DATE and TIME, these should continue to be used unless further notified.

References:
The e-GIF version approved for use in NHS England is:
Government Data Standards Catalogue: (GDSC), Version 1.0, Agreed 1 January 2002.
Further information can be found on the Cabinet Office website.