Over the course of League of Legends, we released hundreds of different codes for various champions and skins. Some of our older code cards did not have expiration dates, however in order to prevent fraud, we have retired all codes created before April 2014. If you have a code card that you got before April 2014, you will not be able to redeem it in the store.
Recent code cards (e.g. Arctic Ops Varus, Riot Fist Bump Ward Skin) have a distinct expiration date and must be redeemed by that date.
If you have an older code card (from before April 2014) and can provide us with the information that we normally request in these situations, we should be able to help you out, provided that you can submit all the required information to us before July 23rd 2014.
Mine are AFTER April - they're from MAY.
End of story.