Is there a Python function to determine which quarter of the year a date is in?

Question

Given an instance x of datetime.date, (x.month-1)//3 will give you the quarter (0 for first quarter, 1 for second quarter, etc -- add 1 if you need to count from 1 instead;-).

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Originally two answers, multiply upvoted and even originally accepted (both currently deleted), were buggy -- not doing the -1 before the division, and dividing by 4 instead of 3. Since .month goes 1 to 12, it's easy to check for yourself what formula is right:

for m in range(1, 13):
  print m//4 + 1,
print

gives 1 1 1 2 2 2 2 3 3 3 3 4 -- two four-month quarters and a single-month one (eep).

for m in range(1, 13):
  print (m-1)//3 + 1,
print

gives 1 1 1 2 2 2 3 3 3 4 4 4 -- now doesn't this look vastly preferable to you?-)

This proves that the question is well warranted, I think;-).

I don't think the datetime module should necessarily have every possible useful calendric function, but I do know I maintain a (well-tested;-) datetools module for the use of my (and others') projects at work, which has many little functions to perform all of these calendric computations -- some are complex, some simple, but there's no reason to do the work over and over (even simple work) or risk bugs in such computations;-).

IF you are already using pandas, it's quite simple.

import datetime as dt
import pandas as pd

quarter = pd.Timestamp(dt.date(2016, 2, 29)).quarter
assert quarter == 1

If you have a date column in a dataframe, you can easily create a new quarter column:

df['quarter'] = df['date'].dt.quarter

I would suggest another arguably cleaner solution. If X is a datetime.datetime.now() instance, then the quarter is:

import math
Q=math.ceil(X.month/3.)

ceil has to be imported from math module as it can't be accessed directly.

For anyone trying to get the quarter of the fiscal year, which may differ from the calendar year, I wrote a Python module to do just this.

Installation is simple. Just run:

$ pip install fiscalyear

There are no dependencies, and fiscalyear should work for both Python 2 and 3.

It's basically a wrapper around the built-in datetime module, so any datetime commands you are already familiar with will work. Here's a demo:

>>> from fiscalyear import *
>>> a = FiscalDate.today()
>>> a
FiscalDate(2017, 5, 6)
>>> a.fiscal_year
2017
>>> a.quarter
3
>>> b = FiscalYear(2017)
>>> b.start
FiscalDateTime(2016, 10, 1, 0, 0)
>>> b.end
FiscalDateTime(2017, 9, 30, 23, 59, 59)
>>> b.q3
FiscalQuarter(2017, 3)
>>> b.q3.start
FiscalDateTime(2017, 4, 1, 0, 0)
>>> b.q3.end
FiscalDateTime(2017, 6, 30, 23, 59, 59)

fiscalyear is hosted on GitHub and PyPI. Documentation can be found at Read the Docs. If you're looking for any features that it doesn't currently have, let me know!