Important: #103496 - ISO format used for date rendering 

See forge#103496

Description 

The default format for date rendering configured in $GLOBALS['TYPO3_CONF_VARS']['SYS']['ddmmyy'] has changed.

The former arbitrary 'd-m-y' format was replaced with the standard ISO 8601 'Y-m-d' format.

Examples of dates where the 'd-m-y' format led to unclear dates:

  • A 2-digit year could also be a day in a month: 21-04-23 could be understood as 2021-04-23 instead of 2023-04-21.
  • The century of years could not be distinguished: 21-04-71 could be 2071-04-21 or 1971-04-21

This affects date display in various locations so code relying on the previous format (e.g. acceptance tests) must be updated accordingly.