Popular Science: A consistent bedtime is critical and there is good quality data that shows regular bedtimes help improve sleep.
Once a bedtime is set, you can develop a routine around it. Research by psychologist Jodi Mindell and colleagues at the Children’s Hospital of Philadelphia has demonstrated how a three-step bedtime routine is helpful. In their study, 199 mothers and their toddlers (aged 1.5 to 3 years) were randomly assigned to one of two groups. One group followed their regular bedtime routine, and the other group was instructed to implement a specific routine consisting of a bath, applying lotion, and a quiet activity. The time between the end of the bath and lights out was 30 minutes.
After two weeks, the toddlers practicing the three-step routine not only fell asleep faster, they had fewer and shorter nighttime awakenings. Interestingly, when the researchers later analyzed infants and young toddlers (aged 7 months to 1.5 years) following the same routine, they found that the most significant effects of improved sleep appeared after just three days.