When Sun-Jay was 2 years old, he began using the word yestertime like a normal word in full and long sentences to include the information that what we were talking about had already happened, but he either didn't know, didn't know how to say, or felt he didn't need to give the date because it already happened and therefore should not be the focus of a conversation trying to determine what best there is to do right now for a future together that maybe also happens to share the singularly present-tense idea of real joy with many people as possible.
For example, I could say to him, "remember yestertime when you had your 4th? birthday and you walked around the indoor playground pretty much ignoring all your classmates while making sure not to let go of the hand of Alice V..." (gee, honesty, I only accurately can say I recall the last name there.)
Remember yestertime, we got a floating balloon on a string from Golden Griddle at the Koslov mall in Barrie, and we were walking through the mall and say a girl just staring at the balloon... and we gave it to her after you made sure we could (and did) get another right away? Remember how unbelievably surprised that little then maybe 3-year-old was? You were so little, but you were so willing to share! And, we can ALWAYS go buy a helium balloon at a flower shop for you if you're wanting to do it again! In fact, we can just buy two, at the time for a buck each--a bargain for priceless joy.