How to Change Week Start Date in Tableau

Your team calculates weekly performance from Monday to Sunday, but Tableau's default graphs stubbornly start the week on Sunday. This small misalignment can cause big problems, from skewed weekly reports to confusing stakeholder presentations. This tutorial will walk you through several easy ways to change the week start date in Tableau, ensuring your data visualizations match your business reality.

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Why Is Changing the Week Start Date in Tableau Important?

Aligning your dashboard's calendar with your company's operational calendar is more than a cosmetic fix, it’s fundamental to data integrity. Many businesses operate on a Monday-to-Sunday workweek. Sales goals, marketing campaign performance, and project sprints are often tracked within this timeframe. If your reporting tool uses a different calendar, you can run into several issues:

• Inaccurate Weekly Comparisons: Calculations like "this week vs. last week" will be incorrect if your definition of a week differs from Tableau's. A spike in sales on a Monday might be attributed to the previous week, hiding valuable insights.
• Confusing Visualizations: When a chart shows a "week" starting on Sunday, it creates a mental disconnect for users who are used to a Monday start. This can lead to misinterpretation and a general lack of trust in the data.
• Misaligned KPIs: If your company's Key Performance Indicators (KPIs) are based on a Monday-start week, your dashboards must reflect that to provide a true picture of progress toward your goals.

Getting this setting right is a basic but essential step in building reliable and useful dashboards.

Method 1: The Quickest Fix Using 'Date Properties'

If you want to set a default week start date for your entire data source within your Tableau workbook, this is the simplest and fastest method. It tells Tableau how to interpret all date functions and aggregations at a workbook level.

Follow these steps:

1. Navigate to the Data Pane on the left side of your workspace.
2. Locate the data source for which you want to change the date settings.
3. Right-click on the data source name.
4. From the context menu, select Date Properties...
5. A dialog box will appear. Here, you'll see several options for configuring dates. Find the "Week start" dropdown menu.
6. Click the dropdown and select Monday (or any other day you need).
7. Click OK.

That's it. Tableau will now recognize Monday as the first day of the week for any weekly visualizations or calculations you create using this data source. When you drag your date field onto a shelf and select the "WEEK" date part, the groupings will now correctly start on Mondays.

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When to use this method:

This is the best choice when a single, consistent week start day applies to almost all the reports you'll build within that specific Tableau workbook. It’s a "set it and forget it" solution.

Method 2: Gaining More Control with Calculated Fields

Sometimes, a global setting isn't flexible enough. You might need to analyze data with different weekly start days in the same workbook, or you might prefer the explicit clarity that a calculated field provides. In these cases, creating a calculated field to define the week's start date is the better approach.

Here are two powerful ways to do it, with the second one being the most recommended for its simplicity and elegance.

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Using the DATETRUNC Function (Recommended)

The DATETRUNC function is the cleanest and most intuitive way to handle this. It truncates a date to the first day of a specified date part (in this case, 'week'). A huge advantage of DATETRUNC is that it includes an optional [start_of_week] parameter.

Here’s how to create a calculated field that forces the week to start on a Monday:

1. Open the calculated field editor by selecting Analysis > Create Calculated Field...
2. Give your calculated field a descriptive name, like "Week Start (Monday)".
3. Enter the following formula:

DATETRUNC('week', [Your Date Field], 'monday')

Simply replace [Your Date Field] with the actual name of your date field, such as [Order Date] or [Ship Date]. Click OK.

You now have a new date field in your Data Pane. When you use this calculated field in your visualizations, it will always return the date of the Monday for the week that the original date falls into. For example, if a record’s date is Wednesday, October 25, 2023, this formula will return Monday, October 23, 2023.

Why this method rocks:

• Clarity and Readability: The formula is self-explanatory. Anyone looking at it instantly knows what it does.
• Flexibility: Need to change it to a Tuesday start? Just change 'monday' to 'tuesday'. You can easily create multiple calculated fields for different scenarios if needed.
• Reliability: It's a precise and standard function that works across different types of data sources without compatibility issues.

Using an Alternative WEEKDAY Calculation

Before the [start_of_week] parameter was added to DATETRUNC, this was a more common method. It combines the WEEKDAY() and DATEADD() functions to achieve the same result. It's useful to know, but generally, DATETRUNC is superior.

The logic is to identify the official weekday number (e.g., Monday=1, Tuesday=2) and anachronistically subtract the appropriate number of days to get back to Monday.

Here is the formula for a Monday start:

DATEADD('day', 1 - WEEKDAY([Your Date Field], 'monday'), [Your Date Field])

Here’s a quick breakdown of how it works:

• WEEKDAY([Your Date Field], 'monday'): This part returns a number from 1 to 7, where 1 is Monday and 7 is Sunday.
• 1 - WEEKDAY(...): If the date is a Wednesday, WEEKDAY returns 3. The formula becomes 1 - 3 = -2. If the date is a Monday, WEEKDAY returns 1, and the formula is 1 - 1 = 0.
• DATEADD('day', ...): This function then adds the result to the original date. For Wednesday, it adds -2 days, pushing the date back to Monday. For Monday, it adds 0 days, keeping it on Monday.

While effective, this calculation is more complex and harder to read at a glance than the simple DATETRUNC approach.

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Verifying Your Changes and Common Pitfalls

After implementing one of these methods, you should quickly verify that it's working as expected. The best way is to build a simple table.

1. Drag your original date field (if you used Method 1) or your new calculated field (if you used Method 2) to the Rows shelf.
2. Right-click the date pill and make sure it is set to Week Number (the discrete, blue pill option like WEEK(Order Date)). This treats each week as a distinct label.
3. To see the full date, right-click the pill again and select Exact Date, then right-click a third time and select Discretize. This ensures each row shows the full Monday date.
4. Drag a measure, like Sales or Profit, onto the Text mark on the Marks card.

You should now see a table where each row's date corresponds to a Monday, confirming your new week start has been set correctly.

Things to watch out for:

• Using Mixed Methods: Avoid changing the Date Properties and creating a calculated field. This can cause confusion. Stick to one method for consistency within a workbook.
• Discrete vs. Continuous Dates: Remember that blue date pills in Tableau are discrete (they create labels), while green pills are continuous (they create an axis). Your grouping can look different depending on which you use. For verifying weekly bins, discrete is often clearer.
• Check Date Formats: When using DATETRUNC or the DATEADD formula, you can format the resulting date by right-clicking the calculated field in the data pane, navigating to Default Properties > Date Format... to change how it is displayed.

Final Thoughts

Correcting the week start date is a small tweak that delivers a significant impact on the accuracy and readability of your Tableau reports. Whether you use the simple 'Date Properties' setting for a global fix or craft a flexible DATETRUNC calculated field for more granular control, you now have the tools to make your dashboards reflect your business cadence precisely.

Manually configuring properties and writing formulas in Tableau is standard practice, but it's often the small, repetitive tasks that consume the most time during analysis. We built Graphed to remove this friction by connecting your data sources and letting you use natural language to get answers. Rather than finding menus or writing calculations, you can just ask, "Show me weekly revenue this year starting on Mondays as a bar chart" and our AI-powered analyst builds the right visualization for you in real-time, completely skipping the manual setup.