You can create a custom folder on the SD card in the canon menu, but would have to do this everytime you shoot, option 2 hit "manual reset" on the file numbering option in the menu each time you shoot.
Option 3, as Ameerat says, when viewing your files in Explorer, sort them by date created and all the images of the same date will be grouped together.

And last but not least, and certainly my preferred method is to format your card each time you take new photos and download them as soon as you get home