Power Query date format (How to + 5 tricky scenarios)

One thing that continually causes problems for all data professionals is dates. Over time, Microsoft has given us a plethora of tools and Excel functions for handling dates, yet they still catch us out. Power Query is a tool for manipulating and cleaning data, and it has a lot of features for managing dates. The Power Query date format is flexible and can be converted into many other text and numeric formats.

For this post, we begin by looking at the basics of Power Query date formats. Then once we’ve grasped that, we move on to look at some tricky date format scenarios.

Download the example file: Join the free Insiders Program and gain access to the example file used for this post.

File name: 0043 Power Query Date Formats.zip

In this section, we look at the basic process and simple transformations for working with dates.

When we get our data into Power Query, we first need to ensure dates have the correct data type. Sometimes Power Query’s automatic detection of data types gets it wrong, so we need to check that all columns are correct.

To change a specific column into a date format, we have lots of options:

Changing the data type is the most important step. Until the columns are recognized as dates, Power Query cannot use them as dates.

One confusing aspect is that Power Query data types exist in two ways:

Value level: Each value in Power Query has a data type. If the column data type shows abc123 (which is the any data type), each value in that column still has it’s own data type (text, number, date etc). The value type determines the type of transformations that can be performed on the value.

Column level: The column data type determines how the contents of a column is understood. The column data type declares that the values within that column should conform to that data type; therefore the actions available are based on that type.

If we write the M code ourselves, it is possible to have a date column that does not contain all date values.

From a date column, we can extract other information. The Power Query date formats available from the ribbon are shown below.

These are available in Power Query’s Transform and Add Column ribbons. The Transform ribbon converts the selected column while Add Column creates a new column based on the selection.

The following are examples of the types of information we can extract from the date column (Year, Days in Month, Week of Year, Day Name, Day of Year)

Each of the transformations above, apply a Power Query function to extract the information from the date. For example, the M code to add the Year and Day of Year columns are:

Year

The Date.Year function extracts the Year from a date.

Day of Year

The Date.DayOfYear function calculates the year day number from a date.

Additional information:

The biggest issue we typically face is getting values into a date type initially. Often this occurs when working with different country date formats.

The date format used in the US is month – day – year. Yet, it is day – month – year in the UK. Then there is the ISO 8601 format, which is year – month – day. 

Personally, I prefer the year – month – day format as it can be sorted correctly when it is text or numeric. But I can’t imagine the UK government is about to change anything on my account.

If using data containing dates in a format different from our local settings, Power Query can get confused. For example, if the cell value is 01/02/03, it could be:

In this section, we look at how we force Power Query to understand dates, even if different country date formats are used.

Look at the screenshot below. It shows dates in five different formats (without any data types applied). I have included the format in the header so you can see what the date format is meant to be.

NOTE: I am based in the UK. My regional settings are set to English (United Kingdom), so the dd.mm.yyyy is the expected format for dates. Depending on your location settings, you may get different results to those shown below.

If I use this data and select Date as the column data type, this is the result:

Power Query gives us lots of tools to solve each of these date formats.

If the date is a valid country format, we can explicitly tell Power Query which country to use.

Click the data type icon and select Using Locale… from the menu.

From the Change Type with Locale dialog box, select the following options:

Then click OK to close the window.

Power Query now shows the correct date.

In the previous section, Power Query already got the correct result for the yyyy.mm.dd format, so we can move on to the next column.

To change the yy.mm.dd format, we can select English (Canada) as the locale date format. At the bottom of the window, it displays a sample of formats that are correctly recognized.

The yyyy-mm-dd format is the first item in the list of sample inputs (shown in the purple box above). This order matches our example data. Selecting this option generates the correct values for this column. Power Query is intelligent enough to recognize the separators and create the correct date.

It may take a bit of exploration to find out which locale (if any) match the format we’ve got.

While the yyyymmdd format is in the same order as English (Canada), due to the lack of separators, Power Query doesn’t recognize this as a date. We will come back to this example in a moment.

If a workbook is going to have a lot of dates in a specific region format, we can change the Locale settings for the whole workbook.

Click File > Options and settings > Query Options

In the Query Options dialog box, select Regional Settings > [Required Locale] > OK

This setting applies to the current workbook only.

Once the locale is set, we only need to use the standard date data type and Power Query will apply that locale setting to each field.

We were left with the tricky yyyymmdd format. There are a few options we can try here. The two we are going to look at are:

Our date is in a standard format, so we can apply basic M code formulas to calculate the result.

Click Add Column > Custom Column

In the Custom Column dialog box, I have entered the following formula.

This is constructed using 4 functions:

With this formula, we’ve constructed the date in a UK format using text.

If changing the data type for this new column, Power Query can now easily recognize this as a date.

This formula is specific for this scenario. You will need to change the formula to match your requirements.

Other useful functions for creating date values are:

Column From Examples is a feature that helps to standardize formats with complex structures.

Select the column, then click Add Column > Column From Examples (drop-down) > From Selection

In the column on the far right, we can start typing the date we want to see, then press Enter.

For example, for the value 20170723, I have entered 23/07/2017 as shown by the screenshot below.

Power Query does its magic and creates values for all our rows. Check that these are right. If not, correct any that are wrong; each time we provide more detail, Power Query adjusts its suggested transformation.

This is an advanced tool. If there isn’t enough standardization in the value, Power Query can easily calculate the incorrect results. But for our scenario, it is reasonably straightforward.

Once happy with the format, click OK.

We have seen how to use the Power Query date format to extract additional information from a date. These are quick and easy transformations. However, before we are able to make those transformations, we need the column to be a date data type.

Using different date formats, we were able to get standardized dates from all of them. Therefore, no matter where the data comes from, we can convert it and use it in our local region.

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