Well before children learn to tell the time, they can learn a routine daily schedule. This helps to set their internal body clock and will encourage sleep at the same time each day.
From as early as 6 to 8 weeks, it is possible to introduce a set bedtime, a set wake time, and set nap times. Naps for very young babies could be every two hours from waking, whereas toddlers can follow set clock times. Planned feeding times will also reinforce the daily schedule.
In the first year in particular, things are often unpredictable, and you'll need to flex the schedule. Start with a morning or evening routine, and build on that. Incorporate things that your child does naturally, but try to keep a consistent order.
As long as they're getting enough sleep overall, it's fine wake your child in the morning or after a nap, in order to keep the schedule on track.
For toddlers, schedule nap times and playtimes. Use frequent reminders to let them know what is going to happen next in the day, especially as you lead up to bedtime.
Keep in mind that most behavioral techniques rely on consistency so that both children and parents know what to expect. You may need to try the technique for several weeks before seeing signs of improvement.