2024: Week 11 - 13 months in a year

Challenge by: Jenny Martin

Are you familiar with the argument that there should be 13 months in the year instead of 12? 13 months, exactly 4 weeks long, would account for 364 days of the year and then we'd just have an extra 1 to deal with (or 2 on a leap year!) 

Naturally, my mind goes to building a workflow that let's me investigate which dates would change months. Naturally, Carl's mind starts wondering what the new month would be called, so do let us know your suggestions!


Just a small input this week:


  • Input the data
  • Create a row for each day of the year
    • I've chosen to use 2024 for the challenge so results will be different if you select a non-leap year
  • Calculate the new months of the year such that the first 28 days of the month are month 1, the next 28 days are month 2, etc
    • This will give you 14 months, with the 14th month containing just 2 days
  • Create a new date with the format:
    • New day of the month / New month / 2024
    • e.g. 20/11/2024 becomes 17/12/2024
  • Filter the data to only contain dates for which the month has changed in the new system
  • Output the data


  • 2 fields
    • Date
    • New Date
  • 190 rows (191 including headers)
You can download the output from here. If you want to check your results. 

After you finish the challenge make sure to fill in the participation tracker, then share your solution on Twitter using #PreppinData and tagging @Datajedininja@JennyMartinDS14 & @TomProwse1

You can also post your solution on the Tableau Forum where we have a Preppin' Data community page. Post your solutions and ask questions if you need any help! 

Popular posts from this blog

2023: Week 1 The Data Source Bank

2023: Week 2 - International Bank Account Numbers

How to...Handle Free Text