Our 4 yo goes to bed between 7-8pm and sleeps till about 7am.

Our 17 month old has one day sleep from about 1-3pm. His evening bedtime depends on that sleep, if he has a 30min nap we'll aim to get him ready for bed by say 6.30pm or if he sleeps for 3 hours we don't bother taking him to bed till at least 8pm. He generally takes about 1.5hours to feed to sleep. Then he wakes up for a feed every 2-3 hours and is up for the day at about 8am.