In my Aikido dojo, the number of hours of training is irrelevant. Personal progress is. This is the reason why Sensei just has his secretary write down every day the names of the students who participated in the class. If we want to keep track of our number of training hours, we can write them down at home, in a notebook or on our computer.
My Karate instructor had attendance cards. Each student had a card with his or her name on it. We would take our cards in a box before stepping on the mat, and, at the beginning of the class, the most advanced student would collect them and go put them on Sensei's desk. After the class, Sensei would put a dating stamp on each card, and Sempai would put them back in the box. This way, we could easily see the number of training hours we'd accumulated since our last promotion. After each promotion, we would get a fresh card.
Now, the fun started with the mini pee wees, the four to six year old ones. Some could not yet read their name, especially with the last name showing first, so the sempai in charge of the class would take the card from the box and hand them to the kids. Then, the most advanced of them would experience the glory or collecting the cards and go put them on Sensei's desk. What a thrill!
And it was so funny!