If you are looking to spend less time booking sessions with your clients or choosing the best time to meet, then you might want to use these tools: Calendly and Doodle.
Use Doodle to select the best time.
With Doodle, you can create a poll with times when you are available, and you can share that with the other participants, so you quickly agree on what is the best time.
The advantages of using a tool like this are avoiding emailing each other back and forth to figure out your availability and automatic time zone detection, so everyone knows the correct time every time!
Use Calendly for session scheduling.
With Calendly, things are a bit different. You configure what kinds of sessions you are offering (30 minutes, 1 hour, etc.), the available time slots, and then send that to your customers, who will pick the right time for them.
Using Calendly also takes care of dealing with timezones correctly, and if you connect it with your calendar, it will automatically avoid double booking.
Both these tools have a free plan, and they are a great place to start when you need to schedule meetings or sessions with your clients.