When you set up your schedule for new sod you can set the start date and the end date. The schedule will only run between those dates. You could then use IFTTT to run the schedule as many times per day as you want or set up multiple schedules for each of the specific start times (ie. 7AM, 9AM, 11AM, 1PM, etc). If you use IFTTT it will not respect a rain or climate delay and will not care about time period of 21 days. IFTTT just does what you command it to do without regards to any Rachio constraints.