If you're in Ontario with the new regulation two under two's, it just makes sense to keep track of those ages as they progress monthly. Unfortunately even if you have only two babies if those don't turn two yet then you must wait until they do or look for over two years olds (currently impossible to find). To track only two babies ages I have made a reminder on a white board in my kitchen so every month just change their age (I'm a visual learner so, seeing it every day helps me to remember when my next openings will happen. My board is very handy when I get calls or emails etc.)