Issue #874322, The All Day functionality has been moved into a separate module and hooks were added to make it easier for other modules to inject steps into date processing.

 Issue #1363460, Make sure widget dates do not end up with the current date when they should be empty.

The repeat description was lost by a recent change to the theme that sent the element through the theme twice.

Issue #1338194, Logic for creating end date wasn't taking into account the possibility that a field might have no value2.

Issue #1216878, Re-introduce 'repeat' as a field setting rather than a widget type so people can't try to switch back and forth between repeating and non-repeating dates. Eliminate repeat widgets.

Issue #1234140 by arlinsundbulte, Change terminology in user-facing text from 'From/To Date' to 'Start/End Date'.

Fix some code that was still using the colon separator in the date id when everything else is now using a period.

Get rid of overlapping formatter functionality. There should be a default formatter with the option to choose a date format as a setting, not a formatter for each format. This was a leftover from the D6 functionality.

#1021512 Fields on user that don't show up on registration form still run through hook_field_validate. Don't validate missing values.

Trying to figure out how to get the list of date fields back into the date argument and filter. Something must have changed.

More clean up of formatters and formatter settings, more re-organization to make the code easier to maintain.

With new formatter settings we can simplify date formats. Make the format type a setting instead of having different formatters for each type. We can also add settings for the interval formatter later.

Re-organize all the field hooks into a single file and add the formatter settings form and summary. This will probably see more changes, this is a first pass.