An 18 month old should go to bed by 7:00 PM to 8:00 PM as babies and toddlers need earlier bedtimes than adults because they naturally wake up early.
Although babies and toddlers also have their own unique sleep schedule and wake windows but they should go to bed by 7:00 PM to 8:00 PM at the latest to get enough sleep before they wake up in the morning.
An 18 month old should take at least one nap a day.
The one nap a day that an 18 month old should take should last between 2 to 3 hours.
Some toddlers often still take 2 naps a day although by 18 months of age most toddlers transition to only needing 1 nap a day for to 2 to 3 hours.
However every toddler and child are different and may need 2 naps a day although some toddlers transition to only needing 1 nap a day earlier.
Toddlers also experience sleep regressions around 18 months of age, which can also affect the toddlers nap schedule.
So instead of focusing just on clock time, you should also pay attention to the toddlers "wake windows" which is the amount of time that your 18 month old or toddler is awake between their naps or their last nap and their bedtime.
Look out for sleep cues such as yawning to help you determine when your 18 month old or toddler is tired and in need of a nap.