python中datetime模块

from datetime import datetime, timedelta


if __name__ == '__main__':
    # 当前时间格式化为字符串
    now_str = datetime.now().strftime('%Y-%m-%d')
    print(now_str)  # 2021-04-19

    # 获取当前时间减去3天后的时间
    start_time = (datetime.now() - timedelta(days=3)).strftime("%Y-%m-%d")  
    print(start_time)   # 2021-04-16