If I understand you correctly I think there is a difference here:
- The “Now”-button sets an empty field to the current date
- The “Reset”-button takes a field which has a date already (because it would be populated if
<default></default> exists), but replaces it with a new date based on the contents of
<default> from the content type xml.
The use case I have that led me to suggest this feature is that I have a field in my content type for when the article has been “editorally modified”. This field is set manually, since we don’t want to include changes like fixing typos.
Having a “Now”-button would solve my use case (if it can overwrite the current value), but resetting to
<default></default> might be more powerful for other use cases. Specially when using math like described in the DateTime-input documentation.