You can control how often Acuity offers appointment slots, either across your account or for specific calendars or appointment groups.
How to control start time intervals
There are two ways to control start times: changing the intervals that Acuity uses to generate appointment slots, which will apply as a default across all your calendars and appointment groups, or listing out individual start times for specific calendar or appointment group, which will override the default interval for that specific calendar.
Change start time intervals
Use the Start Time Intervals setting to control how often Acuity offers appointment start times during blocks of time that you're available.
For example, if you are available 2pm-4pm and set this to 30 minutes, Acuity will offer appointments at 2pm, 2:30pm, 3pm, and 3:30pm.
You can set this manually or opt to let Acuity calculate it automatically based on the lowest common denominator of the different appointment lengths you have.
List start times
Edit your availability to list specific start times, separated by commas, for an individual calendar or appointment group. For example, instead of entering your availability as "2pm-4pm", you could enter it as "2pm, 3pm, 3:30pm", and Acuity would offer only those three times as appointment slots.
You can also combine these start times with the default intervals. For example, if you set your start time interval to 30 minutes, then wrote your availability as "11am, 12pm, 2pm-4pm", Acuity would offer appointments at 11am, 12pm, 2pm, 2:30pm, 3pm, and 3:30pm.