$ python -c 'import datetime; print(datetime.date(2019, 3, 12) + datetime.timedelta(days=366))' 2020-03-12
perl6 -e 'say Date.new("2019-03-12").later( :366days )' 2020-03-12 perl6 -e 'say Date.new("2019-03-12") + 366' 2020-03-12
raku -e 'say "2019-03-12".Date + 366' 2020-03-12
ruby -e "require 'date'; puts (Date.parse('march 12 2019') + 366)" 2020-03-12