So I applied for the German Schengen visa recently and got approved. the thing is, in my document I asked for a period of about 20 days from December 11th 2021 to Jan 2022. But the visa came back with "FROM: 12-12-2021". Can I still keep my original itinerary, which has the departure flight on evening Dec 11 (departs at 20:00 from Toronto - it will takes 7-8hrs to land in Frankfurt) and land on the early morning of Dec 12? Would the border police nitpick that part and not allow me to enter my plane?
Your departure date (2021-12-11 20:00 EST) is 2021-12-12 02:00 CET.
The date of arrival (and departure) on the corresponding passport stamp is what counts.
I don't recall any regulation that deals with any timezone difference between WET (Portugal), CET and EET (Finland/Greece), so assume that the local timezone of the country that issues the passport stamp is what counts.