当前日期时间

import datetime
print datetime.datetime.now()
# 2018-05-08 16:53:30.101000

格式化时间

import datetime
print datetime.datetime.now().strftime("%Y-%m-%d %H:%M")
# 2018-05-08 16:54

多加一天

import datetime
print (datetime.datetime.now()+datetime.timedelta(days=1)).strftime("%Y-%m-%d %H:%M:%S")
# 2018-05-09 16:56:07

减一天

import datetime
print (datetime.datetime.now()+datetime.timedelta(days=-1)).strftime("%Y-%m-%d %H:%M:%S")
# 2018-05-07 16:56:59

其他类似

import datetime
in_date = '2016-08-31'
dt = datetime.datetime.strptime(in_date, "%Y-%m-%d")
out_date = (dt + datetime.timedelta(days=2)).strftime("%Y-%m-%d")
print(out_date)
# 2016-09-02

可以把days改为hours minutes，就可以提前XX小时/分钟了。

timedelta([days[, seconds[, microseconds[, milliseconds[, minutes[,
hours[, weeks]]]]]]])

减去一年

import datetime
from dateutil.relativedelta import relativedelta
d = datetime.datetime.strptime('20180131', '%Y%m%d')
print(d) // 2018-01-31 00:00:00
print((d - relativedelta(years=1)).strftime('%Y%m%d')) // 20170131

还可以把years改为months

时区转换

from datetime import datetime
from datetime import timezone
from datetime import timedelta

# 世界标准时间
utc_time = datetime(2019, 7, 30, 7, 50, 0)

# 北京时间UTC+8
cst_time =utc_time.astimezone(timezone(timedelta(hours=-8))).strftime("%Y-%m-%d %H:%M:%S")

参考：

https://docs.python.org/2/library/datetime.html#timedelta-objects
https://dateutil.readthedocs.io/en/stable/index.html