My dd moved to 1 nap in October (16mths) and it was quite erratic for a week or two, mainly because we were trying to figure out the signs. She cried going down for both naps and would cry when I woke her from her naps (was trying to keep her to a schedule); that's when we realised that she was ready.
She wakes up between 6-6.30am, has breakfast at 7am and snack around 9ish then lunch starts between 11.30-12pm.
Lunch is before her nap even at the beginning, but it would be ealier at 11am if she was really tired. At 11.30, she was too tired & cranky to eat. She would nap at 12pm for 2hours.
Now she naps at 1.15pm for 2 to 2 and a half hours (somedays an hr and a half but rarely).