How to Create Calendar Table in Power BI?
Tags: powerbi, businessintelligence, data
Published: 2023-12-27 09:36:32

## Why do you generally need to create a date table in Power BI, while it is not necessary in Tableau?

In Power BI, a date table is necessary because the DAX language does not support built-in date functions, requiring the creation of a date table to perform date-related analysis. In Tableau, no date table is needed as it supports built-in date functions and features for direct use of date fields in analysis.

## How to create a date table in Power BI?

To create a date table in Power BI using DAX, you can follow these steps:

1. Open Power BI Desktop and go to the Modeling tab.
2. Click on New Table in the Modeling tab to create a new table.
    
 
![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/k1bwmi0xgvagqgnfzpax.png)
    
3. In the formula bar, enter the DAX code to generate the date table. Here's an example of the DAX code to create a date table:

```python
Calendar = ADDCOLUMNS (
	CALENDAR (date(2021,1,1),date(2023,12,31)),
	"Year", YEAR ( [Date] ),
	"Quarter", ROUNDUP( MONTH ( [Date] )/3,0 ),
	"Month", MONTH ( [Date] ),
	"Week", WEEKNUM([Date]),
	"Year Quarter", YEAR ( [Date] ) & "Q" & ROUNDUP( MONTH ( [Date] )/3,0 ) ,
	"Year Month", YEAR ( [Date] ) * 100 + MONTH ( [Date] ),
	"Year Week", YEAR ( [Date] ) * 100 + WEEKNUM ( [Date] ),
	"Weekday", WEEKDAY([Date])
    )
```

This DAX code creates a calendar table with additional columns for year, quarter, month, week, year quarter, year month, year week, and weekday.

Here's a breakdown of each part of the code:

1. `Calendar =` : This is the name of the new table being created.
2. `ADDCOLUMNS ( ... )`: This function adds new columns to an existing table.
3. `CALENDAR (date(2021,1,1),date(2023,12,31))`: This function creates a table with a single column of dates, starting from January 1, 2021, to December 31, 2023.
4. `Year, YEAR ( [Date] )`: This creates a new column named Year which extracts the year from the date in the Date column.
5. `Quarter, ROUNDUP( MONTH ( [Date] )/3,0 )`: This creates a new column named Quarter which calculates the quarter based on the month in the Date column. The ROUNDUP function rounds up the result to the nearest whole number.
6. `Month, MONTH ( [Date] )`: This creates a new column named Month which extracts the month from the date in the Date column.
7. `Week, WEEKNUM([Date])`: This creates a new column named Week which calculates the week number based on the date in the Date column.
8. `Year Quarter, YEAR ( [Date] ) & Q & ROUNDUP( MONTH ( [Date] )/3,0 )`: This creates a new column named Year Quarter which combines the year and quarter information.
9. `Year Month, YEAR ( [Date] ) * 100 + MONTH ( [Date] )`: This creates a new column named Year Month which combines the year and month information into a single number.
10. `Year Week, YEAR ( [Date] ) * 100 + WEEKNUM ( [Date] )`: This creates a new column named Year Week which combines the year and week information into a single number.
11. `Weekday, WEEKDAY([Date])`: This creates a new column named Weekday which calculates the day of the week (1 for Sunday, 2 for Monday, and so on) based on the date in the Date column.

In summary, this code creates a calendar table with additional columns to provide various ways of organizing and analyzing date-related data.

## dynamic date table

To create a dynamic date table for the most recent three years, you can use the following code.

```python
Calendar = ADDCOLUMNS (
	CALENDAR(DATE(YEAR(TODAY())-1,1,1),DATE(YEAR(TODAY())+1,12,31)),
	"Year", YEAR ( [Date] ),
	"Quarter", ROUNDUP( MONTH ( [Date] )/3,0 ),
	"Month", MONTH ( [Date] ),
	"Week", WEEKNUM([Date]),
	"Year Quarter", YEAR ( [Date] ) & "Q" & ROUNDUP( MONTH ( [Date] )/3,0 ) ,
	"Year Month", YEAR ( [Date] ) * 100 + MONTH ( [Date] ),
	"Year Week", YEAR ( [Date] ) * 100 + WEEKNUM ( [Date] ),
	"Weekday", WEEKDAY([Date])
    )
```

In the current DAX code, the date range is specified as one year ago to one year ahead using `DATE(YEAR(TODAY())-1,1,1)` and `DATE(YEAR(TODAY())+1,12,31)`. This determines the range of dates included in the dynamic date table.

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