The new calendar can now show a time field which the old calendar couldn't. Unfortunately this new feature is enabled by default which means the calendar now shows a time field for all extensions using it regardless if the field expects a time part or not. This is a wrong behavior due to (at least) two points:

• The attribute is named showtime which implies that if not present it would not show a time. But actually to show the time you can omit it completely and to hide it you need to add showtime="false"
• The default format attribute for the calendar field is %Y-%m-%d, which means it expects only the date.

Summary of Changes

This PR changes the default value for that attribute to false instead of true.

Testing Instructions

• Change for example the article.xml file and adjust the publish_up field (https://github.com/joomla/joomla-cms/blob/staging/administrator/components/com_content/models/forms/article.xml#L102-L109). Remove the showtime attribute.

Expected result

The calendar shows no time field

Actual result

The calendar shows a time field

Further Testing

• Make sure saving works and doesn't give you a warning, especially when testing with another language where the date format is different to english (eg german).
• Test with various combinations of the translateformat, showtime and format attributes. For example removing them all should result in the date only.

Documentation Changes Required

None
Obviously, this is not fully backward compatible with 3.7.0 as it changes the default behavior. Imho it isn't a big deal as it only affects the display of the calendar popup.