What's the simplest way to subtract a month from a date in Python?

Question

If only timedelta had a month argument in it\'s constructor. So what\'s the simplest way to do this?

EDIT: I wasn\'t thinking too hard about this as was poin

Answer 1

I use this for government fiscal years where Q4 starts October 1st. Note I convert the date into quarters and undo it as well.

import pandas as pd

df['Date'] = '1/1/2020'
df['Date'] = pd.to_datetime(df['Date'])              #returns 2020-01-01
df['NewDate'] = df.Date - pd.DateOffset(months=3)    #returns 2019-10-01 <---- answer

# For fun, change it to FY Quarter '2019Q4'
df['NewDate'] = df['NewDate'].dt.year.astype(str) + 'Q' + df['NewDate'].dt.quarter.astype(str)

# Convert '2019Q4' back to 2019-10-01
df['NewDate'] = pd.to_datetime(df.NewDate)