Hi A.! My 18 month old daughter doesn't go to sleep til 9:30. It appears to be her natural schedule and it allows my husband time to play with her since he rarely gets home before 7:30. In this sense it works well for us. The challenge began with she approached 18 months and realized that she could prolong this time to 10:30+. So we began to prep her for bed around 8:30 with PJs, play time and book time. Then just before bed at about 9:15 she brushes her teeth, gives kisses and we settle to sleep. I have also moved my max time for her to end a nap from 6 pm to 4:30pm. If she naps past 4:30 now she won't sleep til 10 or later. I have actually set her nap time to begin by 2pm at latest if she didn't nap or had a short nap in the morning. I have had to lovingly, yet firmly had to tell her, "It's sleepy time, Semira. You need to sleep." After 2-3 times of saying that, she settles into a nap. If she napped well in the morning many times she will not take a nap in the afternoon.
These little adjustments are helping us to reach a consistent bedtime that works for her and our family. If she sleeps too late in the morning it does throw the schedule off a little but we are working on preventing that. Another thing that helped was adjusting when dinner happened for her. For her, dinner around 6:30 and a snack with daddy at around 8 fills her sufficiently til morning and gives her time to digest before bed.
Good luck, J.