The 2-1 nap transition can be easy breezy or painfully challenging. It can happen as early as 12 months (that is VERY rare) or as late as 18/19 months. A child will typically be ready for the switch to just one nap between 15-18 months.
There are 2 ways that a child’s morning nap can disappear. The first way is the way that we all hope our child drops their nap. Basically, a child just stops falling asleep for their first nap at an age appropriate time (9-10am). If this occurs for 2 weeks, you simply stop offering the morning nap and begin offering just one nap at 11:30am. After doing this for a couple of days, you would then move it to 11:45am for a couple of days, then 12pm for a few days. That one nap a day typically starts between 12pm-1pm until the child is around 4 years old. No surprise here, on average most children start their nap at about 12:30pm.
The second way a nap can fade is more common. Basically, the sleep drive is SO strong at 9:00/9:30am, the child continues taking their first nap but then doesn’t fall asleep for the second nap at the appropriate time (between 12:00pm-1/1:30pm). In this circumstance, a parent or caregiver will want to start addressing this change by “capping” (waking the child) the morning nap to be 15-minutes shorter than it has been. If that reestablishes the second nap, stick with this plan. If the second nap still isn’t reestablished, cap the first nap another 15-minutes
If need be, it is okay to continue to cap the first nap to reestablish the second nap until it is only 1 hour. If the child is still boycotting the second nap after their morning nap is just 1 hour, it’s time to drop the morning nap and push for one nap a day that will occur at 11:30am. After 2 days of 11:30am, push for an 11:45am and then a noon nap. Most children will start their one nap a day anywhere between 12pm and 1pm, so it’s simply trial and error to find what time suits their needs the best.