How can I present my schedule in hourly blocks even though my appointments are 50mins?

Hi,

The services I have scheduled are 50mins or 75mins long. However, on my website I'd like for the client to only be able to book on the hour or half hour (allowing a break between sessions).

Currently it shows 7am, 7.50am, 8.40am ... whereas I'd like 7am, 7.30am, 8.00am ... etc - yet keep the sessions noted as 50mins.

Is this possible? How can I do it?

Thank you!!

http://suewhite.com.au/mentoring-bookings/make-an-appointment/