表示时间总共有 3 个相关的类

datetime.date：表示日期，Attributes: year, month, and day。
datetime.time：表示时间，Attributes: hour, minute, second, microsecond, and tzinfo。
datetime.dateime：表示日期和时间，Attributes: year, month, day, hour, minute, second, microsecond, and tzinfo。
datetime.timedelta：表示一个时间的差值

Import

>>> import time as xtime
# datetime.timezone was added in Python 3.2, So it is normal to get an import error in e.g. Python 2.7.
>>> from datetime import datetime, date, time, timezone, timedelta

Unix TimeStamp

import datetime, time
#获取当前时间戳的整数格式，例如：1553669254
ctime=int(time.time())

timestamp = time.time()
datetime.datetime.utcfromtimestamp(timestamp) #根据时间戮创建一个UTC datetime对象

datetime.datetime.fromtimestamp(time.time()) #根据时间戮创建一个 datetime对象

从字符串中解析出datetime 对象

>>> dt = datetime.fromisoformat('2018-09-22')
>>> dt = datetime.fromisoformat('2018-09-22 16:28:22')
>>> dt = datetime.fromisoformat('2018-09-22 16:28:22.666')
>>> dt = datetime.fromisoformat('2018-09-22 16:28:22.666+08:00')
>>> dt = datetime.strptime('2018-09-22 16:28:22', '%Y-%m-%d %H:%M:%S')

指定 datetime 输出格式

from datetime import datetime

# Sample datetime object
date_object = datetime.now()

# Format the datetime object as a string in the format "DD-MM-YYYY"
formatted_date = date_object.strftime("%d-%m-%Y")
formatted_date = date_object.strptime('2019-10-06','%Y-%m-%d %H:%M:%S')

datetime时间对象实例化

# 构造 datetime(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)
>>> datetime(2018, 9, 22, 16, 28, 22)

>>> datetime.today()       # 不包含时区信息的当前时间（Naive time）
datetime.datetime(2019, 10, 19, 10, 23, 38, 117425)

>>> datetime.now()         # 不包含时区信息的当前时间（当不传入 tz 参数时，和datetime.today()没有区别）
datetime.datetime(2019, 10, 19, 10, 23, 38, 117425)

>>> china_tz = timezone(timedelta(hours=8), 'Asia/Shanghai')
>>> datetime.now(china_tz) # 指定时区对应的当前时间

>>> datetime.utcnow()      # 不包含时区信息的当前 UTC 时间
datetime.datetime(2019, 10, 20, 5, 7, 23, 190797)

>>> dt = datetime.combine(date.today(), time(16, 28, 22))
>>> dt = datetime.combine(date.today(), time(16, 28, 22), china_tz)
>>> dt = datetime.fromordinal(736959) # datetime.min以来的天数

datetime对象的类属性

# 类属性
>>> datetime.min         # 0001-01-01 00:00:00
>>> datetime.max         # 9999-12-31 23:59:59.999999
>>> datetime.resolution  # 0:00:00.000001

datetime对象的实例属性

>>> dt = datetime(2018, 9, 22, 16, 28, 22, 999, china_tz)
>>> dt.year           # 2018
>>> dt.month          # 9
>>> dt.day            # 22
>>> dt.hour           # 16
>>> dt.minute         # 28
>>> dt.second         # 22
>>> dt.microsecond    # 999
>>> dt.tzinfo         # Asia/Shanghai
>>> dt.fold           # 0

datetime对象的方法

# 方法
print(dt.date())          # 2018-09-22
print(dt.time())          # 16:28:22.000999
print(dt.timetz())        # 16:28:22.000999+08:00
print(dt.toordinal())     # 736959
print(dt.timestamp())     # 1537604902.000999
print(dt.weekday())       # Monday is 0 and Sunday is 6
print(dt.isoweekday())    # Monday is 1 and Sunday is 7
print(dt.isoformat())     # 2018-09-22T16:28:22.000999+08:00
print(dt.ctime())         # Sat Sep 22 16:28:22 2018
print(dt.strftime('%Y-%m-%d %H:%M:%S')) # 2018-09-22 16:28:22
print(dt.tzname())                  # 时区名
print(dt.utcoffset())               # 相对 UTC 时差
print(dt.dst())                     # 转换为夏令时
print(dt.timetuple())               # 转成 time.struct_time 
print(dt.utctimetuple())            # 转成 time.struct_time 
print(dt.astimezone(timezone.utc))  # 时区转换

比较时间

dt1 = datetime(2018, 9, 22, 16, 28, 22)
dt2 = datetime(2018, 9, 22, 16, 28, 23)
if dt1 < dt2:
    print(f'{dt1} is before {dt2}')

加减时间

# Usage of time deltas (number of days between two dates, add X days to a date, etc.)
from datetime import datetime

# Define two dates
date1 = datetime(2024, 1, 8)  # Example date 1 (current date)
date2 = datetime(2023, 4, 1)  # Example date 2

# Calculate the difference in days
difference = date1 - date2
number_of_days = difference.days

number_of_days

#####################
from datetime import datetime, timedelta

# Define a date
original_date = datetime(2024, 1, 8)

# Number of days to add
x_days = 10  # Example: Adding 10 days

# Add days to the date
new_date = original_date + timedelta(days=x_days)

可能出的问题

上面的本地时间（datetime.datetime.today()），从底层 API实现来说，它会获取本地机器的时间。

而 UTC 时间（datetime.datetime.utcnow()），从底层 API实现来说，其实是在获取本地机器的时间后，根据当前机器设置的时区信息，计算出 UTC 时间。

这意味着，如果你直接修改了本地机器的时间，则通过 Python API 获取到的时间就会是错误的。

Reference

datetime — Basic date and time types - https://docs.python.org/3/library/datetime.html
Python 日期模块 – datetime - https://blog.csdn.net/shangboerds/article/details/82817901

【Python】API - 时间表示