lol, my dog can tell "time".
If you train your dog at same time every day, like 5pm every day,
is good chance, i'd bet, that before too long, your dog will come pester you for his "lesson" at 5pm.
the same way your dog lets you know it's his dinner time, or time for his walk, etc etc.
If you take your dog to a park, or some place that your dog REALLY LOVED, at say, 2pm, watch the next day, at 2pm,
watch to see if your dog comes up to you, with pleading eyes, or nose=poking, or whatever, at 2pm, as if to say, "It's 2pm! It's 2pm! Are we going to that park again? huh? huh? Are we? It's 2pm! come on, let's go!!"
I am not like Fickla, i do sometimes train my dog if he pesters me, but more often i train my dog when i feel like it, ----------but, either way--------- i use tons of enthusiastic praise, tons of it, and my dog ADORES his lessons, and gets VERY VERY tail-waggy if i even pick up my clicker.