%Y
Year with century as a decimal number.
0001, 0002, …, 2013, 2014, …, 9998, 9999
from datetime import datetime
print(datetime(9, 6, 7).strftime("%Y-%m-%d")) # 9-06-07
print(datetime(99, 6, 7).strftime("%Y-%m-%d")) # 99-06-07
print(datetime(999, 6, 7).strftime("%Y-%m-%d")) # 999-06-07