How do I know the right time to take dad out for the day from the memory care assisted living facility?

Could you ask him those questions? Such as "Dad, we would like to take you out for lunch or a drive, would you like to go?" He will let you know :-)

Thank you for taking the time to reply. We do ask and we can't seem to get an answer either way from him. We try to encourage him, but he seems content with being in his room and the activities they have there. That is his routine. The place he is at is fantastic and the people are wonderful, too.

Then maybe you have your answer :-) Sometimes it is more difficult for us as "the kids" to accept that we are not needed by the parents like we use to be. Trust me, consider yourself (and your dad) very lucky that he has taken to his new home in such a positive way, this is not the norm. I hope I am half as lucky when I have to place my mum in a care home.
You could still ask him if he wants to go out but if you don't get much of a response have peace of mind knowing that he is happy in his new environment.
I wish you and your dad all the best !

I knew in my heart that was probably the answer, but hearing it from someone else helps so much. I love this forum! It is hard to know sometimes. You said it best when you mentioned about it being more difficult to accept we are not needed by parents like we used to be. We are beyond blessed that my dad has transitioned to his new home so well. It was truly an answer to prayer. Awesome place, Awesome people...that makes such a big difference as well. And what a difference and peace of mind it made in my mom's life in the 2 short months he has been there. Thank you again for taking the time to answer. You'll never know how much I appreciate it!