Ingame there seems to be no way to delete savegames. However, it is possible to write new savegames over older ones. Just select the one you would like to overwrite and click the save button.

Although it is also possible to delete the actual savegames in the gamefolder under: Users\Profile1. The files are named like: Save.001, Save.002, etc. However, I recommend against doing that as it seems to mess up your savegames if you delete random savegames there. (Although I didn't seem to encounter any problems if I only deleted the last one.)

The savegames are indeed named after the date and time and I doubt there's any way to name them differently.