from datetime import datetime
from datetime import timedelta

def get_date(days ):
    return datetime.now() - timedelta(days=days)

print(get_date(300).strftime("%Y-%m-%d %H:%M:%S"))

#该函数表示两个时间的间隔
#参数可选、默认值都为0：datetime.timedelta(days=0, seconds=0, microseconds=0, #milliseconds=0, minutes=0, hours=0, weeks=0)