Python3时间戳如何应用于数学计算？

# 文件名：count_days.py
import time
import datetime
def time_controller(d=0, hour=0, minute=0, second=0, arg=1, day=datetime.datetime.now()):
    # 获得某天的x天、y小时、t分钟、z秒后的日期, day为空默认为当前时间开始
    # 所有参数默认都为0，只需要调你需要的时间即可
    # arg = 1: 获得hour小时,minute分钟,second秒后的具体时间
    # arg = -1: 获得hour小时,minute分钟,second秒前的具体时间
    now = datetime.datetime.now()
    if type(day) == str:
        now = datetime.datetime.strptime(day, '%Y-%m-%d %H:%M:%S')
    if arg == 1:
        value = now + datetime.timedelta(days=d, hours=hour, minutes=minute, seconds=second)
    elif arg == -1:
        value = now - datetime.timedelta(days=d, hours=hour, minutes=minute, seconds=second)
    return value
print(time_controller(d=10, hour=20, minute=10, second=0, arg=-1, day='2019-08-01 10:00:00'))
print(time_controller(d=10, hour=20, minute=10, second=0, arg=-1))