the calendar is near the inside of the front door. If it’s Monday then put whichever cow to milk on the Tuesday. Go to sleep then meet them on Tuesday go to the milking area in the portal outside. Talk to the cows to milk them
I have not played this game in quite awhile. I can’t remember if you need to have a certain amount of points to unlock the milking. Or did you need to buy the milking station and build the fence. Or you may have to unlock a scene in the city or near the lake/pond. It will be a few days before I’m able too restart this game to see what I needed to do to unlock the milking. Your best bet is ask on the discord server if not then check past post more than likely someone else had the same problem at one time. You could also ask in any of the players that post on here that look like they are past where you are stuck if they could help you.