By default appointo shows the time in the customers timezone. This helps in easy identification of the time for the customer and allows them to set the right time based on their timezone. However if you want to show the customers the time in your timezone irrespective of where they are you can do that through Appointo.
Please go to General Settings > Store Settings > Scroll down and enable 'Lock Timezone'
Here is a video that will help you understand it better: