The latter could be made even better for newbies, by an "upload to this category" button when looking at a category. My hope is that it would increase the fraction of categorized uploads. Yes, it would also increase the fraction of poorly categorized uploads, but a poor cat is usually better than none. Jim.henderson (talk) 12:46, 9 June 2016 (UTC)
Today's date is currently highlighted in the dropdown calendar (screenshot: File:DateInputWidget active, empty.png). But I'm not sure how this would help with what you want? If you want not to specify the creation date of your upload, just write "unspecified", or maybe only provide the year (you can toggle the date field between the "calendar" mode and the "arbitrary input" mode using the selector to the left of it).
You can already add the same categories and dates to all images by filling them in for the first one, then using the "Copy information to all uploads following ..." menu below it (select the checkboxes for date and categories, unselect the remaining ones, and click "Copy").