Most of the HTC clock widgets on my device also show the date, but I'm using a HTC One, so you may have different widgets available on yours. Try adding a clock widget though, and seeing what options are available to you.
If not, there are very many clock widgets in the Play Store which can do this. I currently have UCCW, Zooper and Minimalistic Text on my device, all of which can show the date (and other information) in many different styles.