To correct one thing he said in case you own more affordable autos like Seiko 5 or Orient 3stars, if the date is half changed it does not mean a tooth broke. It just means it can take about 4 hours to fully change the date, usually from 10 PM to 2 AM
I have had my automatic since 2002. I thought I broke the winding mechanism by shaking it too much around 2006. It became a dust collector in my dead battery watch pile. I ordered a watch repair kit to change batteries for 15 dollars. I though I might take the back off and peek in, give a little lube and see what happens. RU-vid has enabled me to attempt any repair myself.