python123的答案

import datetime

import sys

def next_day(date_str):

date = datetime.datetime.strptime(date_str, '%Y-%m-%d')

date += datetime.timedelta(days=1)

return date.strftime('%Y-%m-%d')

def prev_day(date_str):

date = datetime.datetime.strptime(date_str, '%Y-%m-%d')

date += datetime.timedelta(days=-1)

return date.strftime('%Y-%m-%d')

while True:

line = sys.stdin.readline()

line = line.strip()

if line == '':

break

print('前一天:', prev_day(line))

print('后一天:', next_day(line))