"That day, we laughed a lot together!"
Translation:Ce jour-là, nous avons beaucoup ri ensemble !
But we use years differently. "Cette année-là" means sometime during that year, not on that year.
In my opinion, "Cette journée-là" is not actually incorrect, given that Duo has omitted the word "On". It just means "During that day, …" as opposed to "On that day, …".
But it is not what would conventionally be used in this kind of sentence.