During the early years of life, nap schedules are in a continuous state of change. After a newborn period of all-day napping, babies eventually settle into a regular two-nap-a-day routine.

Most children switch from these two daily naps to one nap sometime between the ages of 12 and 24 months. However, that year of difference is a very long span of time. This shows that age is not the only factor to consider when changing your baby’s nap routine.

Changing your baby from two daily naps to one nap isn’t about what your child thinks he wants, nor is it about the schedule you’d like to have. It’s about the biological need for two naps versus one.

Naps at different times of the day serve different purposes in mind and body development at different ages. For example, morning naps have more dreaming, or REM sleep, which makes them important for young babies who require it for early brain development. You don’t want to rush the process if your child is still benefiting from this important sleep time.

There is another consideration when deciding to make a schedule change—the length of time your child is awake from one sleep period to the next has an effect on his mood and behavior.

No matter how well your baby sleeps at night, naps are still very important. The older your child is, the longer he can go between sleep breaks without getting cranky. The biology behind this reason dictates that young babies need to divide their day up with two naps, but older babies and toddlers can handle a full day with only one nap.

Since there is a wide range of what’s normal, it’s important to study each child’s behavior to see when he is ready to transition to one nap a day. Use the following lists as a guide.

6 signs that your child needs two naps daily

Your child is under 12 months old.
When you put your child down for a nap they play, resist or fuss for a while, but always end up sleeping for an hour or more.
When you take your child for car rides during the day they usually fall asleep.
If your child misses a nap, they are fussy or act tired until the next nap or bedtime.
Your child is dealing with a change in their life (such as a new sibling, sickness or starting daycare) that disrupts their nap schedule.
Your child misses naps when you’re on the go, but when you’re at home, they take two good naps.

4 signs that your child is ready to change to one daily nap

When you put your child down for a nap, they play or fuss before falling asleep, and then takes only a short nap, or never falls asleep at all.
Your child can go for car rides early in the day and not fall asleep in the car.
When your child misses a nap, they are cheerful and energetic until the next nap or bedtime.
Your child naps well for one of their naps, but totally resists the other nap.

How to make the transition when signs point to change

Instead of thinking in terms of dropping a nap, it’s better to think in terms of a schedule change. The change from two naps to one nap is rarely a one-day occurrence. Most often, there will be a transition period of several months when your child clearly needs two naps on some days, but one nap on others.

You have a number of options during this complicated nap transition time

Watch for your child’s sleepy signs, and put your child down for a nap when indications first appear.
Keep two naps, but don’t require that your child sleep at both times, allow quiet resting instead.
Choose a single nap time that is later than the usual morning nap, but not as late as the afternoon nap. Keep your child active (and outside, if possible) until about 30 minutes before the time you have chosen.
On days when a nap occurs early in the day, move bedtime earlier by 30 minutes to an hour to minimize the length of time between nap and bedtime.

The danger of dropping a nap too soon

It’s my belief that many of the behavior issues during the toddler years (see: the “Terrible Twos“) are very likely caused by inappropriate napping schedules. There are a great number of toddlers who switch from two naps a day to one nap, or drop naps altogether, many months before they are biologically ready. This can result in a devastating effect on their mood and behavior—the dreaded “Terrible Twos.”

For those parents whose children suffer the “Threenager Years” or the “Fearsome Fours,” it’s likely your child is misbehaving for the same reason—an inappropriate nap schedule may be the culprit.

The good news is that a modification of your child’s napping routine can make a wonderful and dramatic difference in his day—and yours.

This article has been excerpted from “The No-Cry Nap Solution: Guaranteed Gentle Ways to Solve All Your Naptime Problems” by Elizabeth Pantley (McGraw-Hill, January 2009). It was originally published on Nov. 21, 2017 and has been updated.