Virtually any major carrier anywhere will, at a minimum, require fare class availability to confirm a change for free, even day of departure. TG, like other carriers, will certainly allow you to standby if there is no such availability. If you want to confirm without fare class availability, you'll have to pay up.

And the notion that European carriers are somehow more flexible on same day changes is just wrong. Ask LH for a free same day change and see how that works for you.