A Short Rant

My boyfriend is usually very sweet, there is just one thing he does that really gets to me. He can make plans, seemingly without any regards to me. I always take his schedule into account, but today he made dinner plans with a mutual friend of ours (who I'm slowly growing less fond of...) Before he did that I asked him how long he could stay that day, since that would be the day after our date night. And he said he should get home around five,,, but then he goes and makes these plans, which are obviously for the evening.

And this is not the first time that he does this type of thing, but he suggested the date night which was sweet of him.

We've been together for three years now, but he's leaving soon and he'll be gone for six months, so I don't want this to be a "thing"... Any advice?