If, like me, you’re a little new to the world of data visualisation and Tableau, you might have noticed things behaving a little strangely when working with time-based data. Your time lines might look broken, or your charts don’t flow the way you expect, and you’re faced with the question of discrete or continuous dates, blue pill vs green pill?
So what is the difference between the two and when should you use each one?
Discrete dates (blue pills) treat your date field as a set of separate categories, rather than a single continuous timeline. Tableau splits time into distinct parts (like months, quarters, or years) and creates individual headers for each period. This lets you compare specific chunks of time side by side, for example, “October vs November” or “2024 vs 2025.”
Behind the scenes, Tableau uses the DATEPART() function to extract the chosen time period (e.g. month, quarter, or year) and then groups all the data that falls into that bucket.
Example:
If you’re looking at Sales by Month, Tableau groups all the October sales together, all the November sales together, etc, allowing us to compare them side by side, typically as a bar chart.
Think of discrete dates as buckets of time. Tableau counts or sums the data inside each bucket so you can easily compare one period with another. We use discrete dates to see how different parts of time compare against each other.
On the other hand, continuous dates (green pills) treat time as an unbroken timeline. Instead of headers for each month or year, Tableau creates a timeline axis that lets your data flow smoothly from one period to the next. This allows us to see trends over time, seeing how values rise and fall across time.
Tableau uses the DATETRUNC() function to roll dates up to the start of a specific period (month, quarter, year), where it can then aggregate all data within that period, for example summing all October sales into a single point that represents the total for the month.
Example:
Tableau plots a single data point per month (using the rolled-up dates) and connects them along the x-axis — from January → February → March → April — creating a continuous flow to show the overall trend.
Think of continuous dates as a smooth line that never breaks. Rather than comparing distinct chunks of time, continuous dates help you see how your data moves and changes across the entire timeline.
I hope this helps you make sense of those blue and green pills next time you’re building a chart in Tableau. At the end of the day, it all comes down to one simple question: do you want to compare time periods or show how things change over time?
Once you understand how Tableau handles these two types of dates, it becomes much easier to choose the right chart for the story you want to tell.
Here’s the quick way to think about it:
- Discrete (blue) → breaks time into separate buckets so you can compare one period against another.
- Continuous (green) → treats time as a flow, showing how things change across the timeline.
Use discrete when you want clear, side-by-side comparisons “Which month performed best?”
Use continuous when you want to see a trend — “How has performance changed over time?”
Once you start recognising when to use discrete vs continuous dates, your visualisations will flow more naturally, and you’ll have way more control over how your data story unfolds.