If the EPG data doesn't have Season and Episode numbers, but does have the Original Air Date (which is saved in the MC tag [Date]), then MC will also fill in the [Year] tag, and that is copied across to the [Season] tag, leaving the [Episode] tag blank.
So what you are seeing is normal when your EPG data doesn't have Season and Episode numbers.
If you are using the SD EPG source, are you using their JSON interface? Only that interface includes Season and Episode numbers I believe. Have a look at the
USA TV Setup thread and search the Television forum for "JSON". You should find some info on getting Season and Episode numbers.