Here is my Flower Farm calculator. All you need to do is enter the time listed on the Event Timer (both days and hours) in the Blue boxes. The spreadsheet will automatically calculate how many refills you need in each of your Farms to last till the end of the Event. Just add to your Farms till your Farms match the calculator. (remember to update time so it is current at each visit)
https://docs.google.com/spreadsheets...BMU/edit#gid=0
This will most likely be usable for future Events without me having to change anything, except maybe the Merchant Only Phase timeframe.