import re

def date_is_right(date):
	return re.match(r"\d{4}-\d{2}-\d{2}", date) is not None

print("2021-05-20", date_is_right("2021-05-20"))
print("202-05-20", date_is_right("202-05-20"))
print("2021/05-20", date_is_right("2021/05-20"))
print("20210520", date_is_right("20210520"))
print("20a10520", date_is_right("20a10520"))