I use 2 excel spread sheets for all my breeding related critical dates. They allow me to drop in a key date such as when I want to lamb or when I plan to put rams in and they fill in all the critical dates for ram MOT, flushing, vacs, feeding etc. I also have columns for earliest date for vacs and latest (4 to 6 weeks before) and it works out my optimum vac dates for the ewes within that band.
I also use a couple of word tables to plot out cohorts for lambing, feeding ration, worming etc with details of weeks to go and info on previous years lambing ( do they tend to lamb early, have triplets, mismother etc.)
The info is partly for me but also incase I was taken seriously ill and OH had to get the vet out. I know they would have all the info that they need.
I then write vac dates and lambing dates on the calendar