Nico has been focusing on time for a while now. He wants to understand all aspects of time; days, weeks, months, years, hours, minutes, and seconds. He loved counting down the days until Christmas, and is now counting down the days until his birthday.
He's already asked about and understands all the basics, such as; How many days in a week/month/year? How many hours in a day? Minutes in an hour? Seconds in a minute? Now he is focusing on learning how to use that information. He is constantly looking at the clock, and watching how it changes throughout the day. Asking how long until his bedtime, or favorite t.v. show comes on? Nico is forever making statements about time, for example; It's 3 o'clock now, and in five hours it will be 8 o'clock. And he's starting to grasp the amount of time it takes to do certain things, such as; It takes 30 minutes to drive to Matthew's house, and 30 minutes to drive home, so we are out of the house for a full hour.
There is still a lot that he doesn't quite grasp. Like, why is Lucas's birthday first, even though he is older? I've tried explaining the cyclical nature of time, and that Lucas's birth came before the end of Nico's second year, but he just doesn't get it, yet. I'm sure given enough time to think it over, he will come to understand.