Converting week numbers to dates

Question

Say I have a week number of a given year (e.g. week number 6 of 2014).

How can I convert this to the date of the Monday that starts that week?

One brute force solution I thought of would be to go through all Mondays of the year:

date1 = datetime.date(1,1,2014)
date2 = datetime.date(12,31,2014)
def monday_range(date1,date2):
    while date1 < date2:
        if date1.weekday() == 0:
            yield date1
        date1 = date1 + timedelta(days=1)

and store a hash from the first to the last Monday of the year, but this wouldn’t do it, since, the first week of the year may not contain a Monday.

Asked By: Amelio Vazquez-Reina

||

Source

Answer 1

All about strptime strftime:

https://docs.python.org/2/library/datetime.html

mytime.strftime('%U') #for WC Monday
mytime.strftime('%W') #for WC Sunday

Sorry wrong way around

from datetime import datetime
mytime=datetime.strptime('2012W6 MON'. '%YW%U %a')

Strptime needs to see both the year and the weekday to do this. I’m assuming you’ve got weekly data so just add ‘mon’ to the end of the string.
Enjoy

Answered By: Malcolm Murdoch

Answer 2

You could just feed the data into time.asctime().

>>> import time
>>> week = 6
>>> year = 2014
>>> atime = time.asctime(time.strptime('{} {} 1'.format(year, week), '%Y %W %w'))
>>> atime
'Mon Feb 10 00:00:00 2014'

EDIT:
To convert this to a datetime.date object:

>>> datetime.datetime.fromtimestamp(time.mktime(atime)).date()
datetime.date(2014, 2, 10)

Answered By: anon582847382

Answer 3

A simple function to get the Monday, given a date.

def get_monday(dte):
    return dte - datetime.timedelta(days = dte.weekday())

Some sample output:

>>> get_monday(date1)
datetime.date(2013, 12, 30)
>>> get_monday(date2)
datetime.date(2014, 12, 29)

Call this function within your loop.

Answered By: Edwin S.

Answer 4

We can just add the number of weeks to the first day of the year.

>>> import datetime
>>> from dateutil.relativedelta import relativedelta

>>> week = 40
>>> year = 2019
>>> date = datetime.date(year,1,1)+relativedelta(weeks=+week)
>>> date
datetime.date(2019, 10, 8)

Answered By: dimosbele

Answer 5

To piggyback and give a different version of the answer @anon582847382 gave, you can do something like the below code if you’re creating a function for it and the week number is given like "11-2023":

import time
from datetime import datetime

def get_date_from_week_number(str_value):
    temp_str = time.asctime(time.strptime('{} {} 1'.format(str_value[3:7], str_value[0:2]), '%Y %W %w'))
    return datetime.strptime(temp_str, '%a %b %d %H:%M:%S %Y').date()

Answered By: Chris

Converting week numbers to dates

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