dateutil库是一个处理时间的工具库。本地自带，一般不用再次安装。

1、直接在某个时间点上直接修改年份、月份等信息。

示例代码：

from dateutil.relativedelta import relativedelta
from datetime import datetime

now_time = datetime.now()
print(now_time)

# 将当前时间年份增加3年或减少3年，
# alter_year = relativedelta(years=-3)
alter_year = relativedelta(years=3)
# aa = now_time - alter_year
aa = now_time + alter_year
print(aa)
# months, weeks, days, hours, minutes, seconds, microseconds方法同years
"""官方文档解释：
years, months, weeks, days, hours, minutes, seconds, microseconds:
            Relative information, may be negative (argument is plural); adding
            or subtracting a relativedelta with relative information performs
            the corresponding arithmetic operation on the original datetime value
            with the information in the relativedelta.
"""
# 将当前时间年份直接更改为某个具体年份
alter_year = relativedelta(year=2010)
# bb = now_time - alter_year
bb = now_time + alter_year
print(bb)
# month, day, hour, minute, second, microsecond方法同year
""" 官方文档解释：
year, month, day, hour, minute, second, microsecond:
            Absolute information (argument is singular); adding or subtracting a
            relativedelta with absolute information does not perform an arithmetic
            operation, but rather REPLACES the corresponding value in the
            original datetime with the value(s) in relativedelta.
"""

运行结果：

2、日期转换，字符串日期转为datetime

示例代码：

from dateutil.parser import parse  # 日期解析器

print(parse("Jul 15 2022 13:00:36"))  # 月份也可全称，如july,January
print(parse('20220717'))
print(parse('2022-07-17'))
print(type(parse('2022-07-17')))

运行结果：

3、计算时间差：如计算一个人出生到现在的时间

示例代码：

from dateutil.relativedelta import relativedelta
from datetime import date

# 1.第一种方式
today = date.today()
print(today)
birthday = date(year=2020, month=1, day=1)  # 假设出生日期为2020-1-1
print(birthday)
diffday = (today - birthday)  # 今天和出生日期计算相差天数
print(diffday)
print(diffday.days)  # 只能计算出天

# 2.第二种方式
# 下面可计算两个日期中间相差几年，几个月和几天
diff = relativedelta(today, birthday)
print(diff)  # relativedelta(years=+2, months=+7, days=+19)  2岁7个月19天
print(diff.years)  # 年
print(diff.months)  # 月
print(diff.days)  # 日

运行结果：

4、获取接下来每周周几的日期

示例代码：

from dateutil.rrule import rrule, WEEKLY
from datetime import date, datetime

next_wednesday = date(year=2022, month=8, day=20)  # 设置下一个周六，2022-08-20
# next_wednesday = datetime(2022, 8, 20)
data = list(rrule(WEEKLY, count=10, dtstart=next_wednesday))
# 上面rrule函数中WEEKLY表示频次，即每周，count表示计算的数据数为10个
# dtstart即起始日 byweekday可以指定MO,TU,WE,TH,FR,SA,SU。即周一到周日。
for one in data:
    print(one, '------>', one.strftime('%Y-%m-%d'))

运行结果：

具体更多功能详见源码。