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# Group dates by month, year or weekday in a pivot

> Set a date column's Edit format in Mammoth Group & Pivot to total by year, month, weekday, day, hour or minute, and see which formats change the column type.
>
> Applies to: Where: View › Describe your transformation › Reshape, Group & Pivot › Group & Pivot › Rows › edit icon

In **Group & Pivot**, a date column in **Rows** or **Columns** is grouped by day unless you change its **Edit format**. Pick a coarser format to total by month, year or weekday. For building the pivot itself, see [Group, pivot and unpivot data](https://mammoth.io/docs/learn/clean-and-shape/group-and-pivot/).

## Choose how dates are grouped

When a date column is in **Rows** or **Columns**, its edit icon opens an **Edit format** list that sets how dates are grouped. The default is by day (**DD-Mon-YYYY**).

| Edit format | Groups by | Result column type |
| --- | --- | --- |
| **DD Mon, YYYY  HH:MM:SS** | Second | Date |
| **DD Mon, YYYY  HH:MM** | Minute | Date |
| **DD Mon, YYYY  HH** | Hour | Date |
| **DD-Mon-YYYY** (default) | Day | Date |
| **YYYY, Month** | Year and month | Text |
| **YYYY** (number icon) | Year | Number |
| **Month** | Month name, across all years | Text |
| **YYYY** (text icon) | Year | Text |
| **Weekday** | Day of the week, across all weeks | Text |
| **Mon-DD, YYYY  HH:MM:SS** | Second, written as text | Text |

A format that isn't a date changes the column's type, and the menu says so before you save, for example: "Editing format of column "order_date", changes its type from "Date" to "Text"". A date column in **Rows** also has a **Display Name** box.

**Example:** to total sales by month, put `order_date` in **Rows**, set its **Edit format** to **YYYY, Month**, and put `sales` in **Values** with Sum.

## Related

- [Group, pivot and unpivot data](https://mammoth.io/docs/learn/clean-and-shape/group-and-pivot/): Rows, Columns and Values.
- [Work with dates and financial years](https://mammoth.io/docs/learn/clean-and-shape/dates/): extract a month or financial year to group by.
- [How the pipeline works](https://mammoth.io/docs/learn/clean-and-shape/how-the-pipeline-works/): the grouping re-runs on every refresh.

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Source: https://mammoth.io/docs/learn/clean-and-shape/group-by-date.md · Updated: 2026-11-08