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Power BI: Making Date & Time Keys

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Saving the Day from Delay Part 2

Creating DateKey and TimeKey columns can be done with built in functions in the Power Query editor. Quick call out, if you need the time along with dates, I highly recommend splitting your datetime columns in half – one date only and one time only. From there, you can use the same process to convert your time to a decimal number and use a Time Table for your time functions (GitHub link below). Below are some screenshots to walk you through the process.

Let’s say you have a datetime column like my Date column below. To start, I recommend going to the Add Column tab in the query editor, and select Date Only then Time Only to create two new columns. This way the new columns will be right next to each other in the applied steps which will make troubleshooting down the road a lot easier. Don’t forget, you can right click on steps and rename them to help yourself walk through and/or adjust steps in the future.

Time to make our keys! There are a couple ways to do this, but the easiest is to click on the calendar icon (or clock icon for time) and select whole number (select decimal for the time only column). If you’ve worked in Excel, this will look familiar. These whole numbers for date (or decimal for datetime) is the same across the two platforms and is what DAX uses in the background to process datetime equations.

Final Date and DateKey Columns
Final Time and TimeKey Columns

And that’s it! Next post we will look at how to join the date and time tables to your keys in the data model.

External Resources:
https://data-mozart.com/inside-vertipaq-compress-for-success/
https://github.com/AnytsirkGTZ/TimeTable_MCode/blob/main/MQuery%20Time

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