https://docs.python.org/ko/3.7/library/datetime.html

96일 차이나고 0이 월요일입니다. 상기 도움말 참고하세요.

In [1]: from datetime import date

In [2]: s_date = date(2020, 1, 1)

In [3]: diff_date = date.today() - s_date

In [4]: diff_date
Out[4]: datetime.timedelta(days=96)

In [5]: target_date = date(2020, 1, 1) + diff_date

In [6]: target_date.weekday()
Out[6]: 0

>>> from datetime import date
>>> s_date = date(1, 1, 1)
>>> diff_date = date.today() - s_date
>>> diff_date
datetime.timedelta(days=737521)
>>> diff_date = date(2020, 3, 10) - s_date
>>> diff_date
datetime.timedelta(days=737493)