Call whenever you want.

I used to wonder if it was too late to call, too early etc.

Then my brain kicked in and I realized that the phone I am calling is their business line. If they are not working they will not answer. Most likely there business phone is turned off until it's time for business I would think.

I called one provider I really wanted to see that travels to Chicago frequently without even knowing she would be here.  She had not posted an ad yet or anything. She picked up. She had just arrived in town and when I got to the incall she mentioned I was her first visitor during hr stay.

The only time I do not call whenever I feel like it is when I have seen an ad previously from a provider that clearly states her hours.