Do we have to train on the same day?

No. You do not have to train on the same day as your friend.

If you train today, your friend has until their own streak would break to train too. When they train, the friend streak goes up by one and they are told it went up.

So one of you can train days after the other and it still counts, as long as their own streak is still alive.

After the friend streak goes up, the next one starts. You both begin again the next day.

Learn more: My friend streak went back to zero