Date field in TV recordings come from the guide. It represents the date (or year) the show was made, or first aired.
I just checked my three recordings since yesterday, they do have full dates:
10/10/2011 (Arthur)
1/1/2017 (From Vienna, the new year's celebration)
3/11/1991 (BBC World News) --------- this one does not make sense, but it is the way the guide is. This date might be the date the show started
It is normal to have date field having only year in it. Again, it comes from the guide.