Describing your child's age can be challenging, especially when talking to those who have not yet had much experience with children themselves. Every so often I'll see a social media post (written or video) complaining that parents are illogical in how they describe their children's ages. A classic one is wondering why parents switch from days to weeks, to months and then years and sometimes back to months. It's a fair question, but their suggestion of just using years is completely unhelpful after even just a few moments of thinking about it.

Most adults use whole numbers of years to describe their age. This makes perfect sense. As I write this I tell people that I'm 58, when in reality I am 58 and 7 months. Like most other adults I just round down. I wont tell anyone I'm 59 until the actual day of my approaching birthday. The reason that this approach is reasonable is that rounding 58 and 7/12 down to 58 doesn't lose much precision. We're dealing with larger numbers and no one really gets that excited about birthdays after 21. (Except my daughter who looked forward to being 25 so she could start saving on her car insurance.)

When we are describing the ages of children, we are dealing with much smaller numbers and a faster rate of change in their development. A year makes a huge difference when observing children. A year really doesn't make difference with me. My height, weight and general feelings about life don't change much across a year. Also, the rounding down thing is tricky, because under a year old, you'd round them down to zero and no one likes being described as zero years old.

When a child is born, we describe them as newborn for at least that day. When they reach the next day, it's appropriate to refer to them as 1 day old. This is preferable to calling them 0.0027 years old. Occasionally they are described as new born for up to a week or two, but that is more of a generic description, given that they are relatively newly arrived in the world, rather than expressing that they are within the day of their birth. For the rest of the week after birth a child is described as days old and then on the 7th day, they are described as a week old. This is appropriate because so many things change in that first week. They learn to breastfeed or take formula from a bottle, they get their digestive system started (yes, that includes learning to pee and poop) and then they learn about day and night and hopefully decide to sleep during the night (not guaranteed and lots of work to reverse the decision to be nocturnal).

On average, most babies sleep a lot for the first six weeks of their life (Except for the ones who don't, of course.) so experienced parents describe their child's age in weeks until they get past this stage. The normal nomenclature after that is to just use months. So after six weeks comes two months, all the way up to eleven months, then it is acceptable to describe your child as one year old. This time period includes all of the events to do with rolling, crawling, teething, sitting, standing and walking. These generally happen at different months, so again, experienced parents use the month number.

As for trying to explain the switch from one year back to months, all I can think of is that enough things are still changing and developing in children of that age that it makes sense to continue using months. Thankfully there does seem to be fairly universal agreement to describe children's ages in whole numbers of years when they reach two years old. (With a few who like to throw an occasional "and a half" in there.)

I hope that this helps anyone out there without much contact with children to understand why those of us who do interact with young children describe their ages in the way we do.