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This is Day 16 of the #100DaysOfPython challenge.

This post will use the standard datetime library to work with dates. The final project code can be found here.


  1. Familiarity with Pipenv. See here for my post on Pipenv.

Getting started

Let’s create the hello-python-datetimes directory and install the required dependencies.

We are now ready to begin exploring the standard datetime library.

Playing around with dates and times

Start the shell with pipenv shell ipython. This will activate the virtual shell and start an iPython interactive shell.

Now we are free to from datetime import date and play around with it:

The above displays some of the common methods of the date class. More information about the date class can be found here.

A lot of what we want to do today is look at how to take some of these methods and get to a point where we can compare dates.

Comparing dates

We want to write a helper method to check if a given date in the format YYYY-MM-DD is before today. Exit the iPython kernel and add the following code to our src/datetimes.py file:

We can use the > and < operators to compare dates.

If we now run python src/datetimes.py we should see the following output:

We can see the output reflects a date string that is before today (with today returning False).

Working with now

The datetime module from the datetime library also has a now method that returns the current date and time.

We can use this in combination with strftime to get the current date and time in a string format. Update the code to the following:

Running python src/datetimes.py will output 2021-08-04 and False respectively.

To learn more about strftime, there is a great blog post here.

Adding and subtracting dates

We can use datetime.timedelta to add and subtract dates.

Update our code to the following:

Once again we will python src/datetimes.py which will output the following:

Awesome, now we know how to add and subtract from dates!


Today’s post demonstrated how to use the datetime module to compare times and determine the current date.

Dates and times are incredibly important to any temporal applications, and the following posts will spend some time looking further into this and how to write tests for this form of functionality.

Resources and further reading

  1. The ABCs of Pipenv

Photo credit: pawel_czerwinski

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Senior Engineer @ UsabilityHub. Formerly Culture Amp.