We don't currently support that, the plan is for schedules to support multiple start times, we are building the infrastructure to support that but it is going to take some time.
In the meantime, this can be achieved using IFTTT.
The recipe 'Run watering time every hour for sod' should work. Create a schedule in our app, disable it, and then let IFTTT run it whenever you want, at whatever hourly/daily frequency.
More about IFTTT and Rachio.
Hope this helps.