I have asked TG in the past about changing time/dates for domestic flights on award tickets issued by LH and SK - even on sold out flights where I was prepared to take a later flight - and every time the answer is that you need to contact the issuer of the ticket to have the ticket changed. TG is not going to touch flights on an award ticket issued by other airline and your chance of TG accepting to change your ticket to a later flight is close to zero. Maybe it would be higher if you asked at the airport to get on an earlier same day flight; but to get on a later flight - forget it!