# Change the period
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Periods are a core concept in Phocas. Read the [Periods](https://app.gitbook.com/s/7pj8v25BOyqZTdG5mdD1/getting-started/periods) page to learn more about the **Period** menu and the different types of periods.
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You use the **Period** menu to change the timeframe that applies to the data in the grid.
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* Flexible Variance mode has three period menus, allowing you to view data for three different periods to the grid.
* If you add a measure column to the grid, you can change the period that applies to its data in the column definition settings.
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## Apply a defined period
Click the **Period** menu to view the list of defined periods, then select the one you want to apply.
The selected period displays in the **Period** menu and the grid updates with data for that date range.
### Add your own defined period
You can’t create [user defined periods](https://docs.phocassoftware.com/analytics/customize-your-view-analytics/change-the-period-analytics#changetheperiod-inanalytics-addauser-definedperiod) in Flex Modes. To use one there, first create it in Analytics. It will automatically flow through and be available in Flex Modes.
## Apply a custom period
1. Click the **Period** menu > **Select dates** option.
2. Select the period type (time unit): **Year**, **Month**, **Week**, or **Day**.
3. Choose whether to apply **fixed** or **dynamic** date range.
* Use fixed when you need precision, repeatability, or historical consistency.
* Use dynamic when you need automation, recency, or ongoing monitoring.
* See below for more details and examples of each option.
4. Select the **Start** and **End** of the date range.
5. Click **Apply**.
Your custom period displays in the **Period** menu and the grid updates with data for that date range.
### Apply a fixed date range
A fixed date range has a set start and end date. The data is always the same, even if you redo the analysis or open a favorite later.
Use cases include:
* An annual sales report for the 2025 financial year.
* Analysis of a marketing campaign that ran from March 15 to April 30, 2025.
* A comparison of sales in January 2024 and January 2025.
For example, suppose you're analyzing your Sales database and want to identify customers who purchased products during the summer season (in the northern hemisphere).
1. Select the **Month** period type.
2. Select June 2025 as the **Start** month and August 2025 as the **End** month.
3. Click **Apply**.
### Apply a dynamic date range
A dynamic date range updates automatically based on when you run the analysis. Common options include *Last 30 days*, *Month to date (MTD)*, and *Year to date (YTD)*.
Dynamic ranges are useful for ongoing monitoring because if you [used in favorites](https://docs.phocassoftware.com/analytics/flex-modes/save-and-share-a-favorite), you always see the latest data without having to reset the period manually.
Use cases include:
* A Sales dashboard showing the last 7 days revenue.
* An Inventory report tracking stock levels in the month to date (MTD) or quarter to date (QTD).
* A weekly performance review always looking at the previous week.
The following examples are common *set-and-forget* dynamic periods you can add to your analysis:
Last month
Suppose today is in the month of September and you want to view the Sales performance of the previous month. Next month (October), you'll want to see September's sales values, and so on.
1. Select the **Month** period type.
2. Click **Use dynamic dates** at the bottom of both the **Start** and **End** calendars. By default, the **Relative** dynamic option is selected for both.
3. Leave **Last month** selected for the **Start**, but change the **End** from **This month** (default) to **Last month**.
4. Click **Apply**.
Rolling 12 months
Suppose today is in the month of September and you want to view sales data for the last 12 months up to today. Going forward, you want to see the past 12 months' sales data on any given day.
1. Select the **Month** period type.
2. Click **Use dynamic dates** at the bottom of both the **Start** and **End** calendars. By default, the **Relative** dynamic option is selected for both.
3. Change the **Start** to **11 months ago** and the **End** to **This month**.
4. Click **Apply**.
Last 3 years
Suppose today is in the month of September and you want to view the sales data for the last 3 years. Going forward, you want to see the past 3 years' sales data on any given day.
1. Select the **Year** period type.
2. Click **Use dynamic dates** at the bottom of both the **Start** and **End** calendars.
3. Change the **Start** to **2 years ago** and the **End** to **This year**.
4. Click **Apply**.
Last 7 days
Suppose today is September 29 and you want to view the sales data for the last week (7 days). Going forward, you want to see the past weeks' sales data on any given day.
1. Select the **Day** period type.
2. Click **Use dynamic dates** at the bottom of both the **Start** and **End** calendars. By default, the **Relative** dynamic option is selected for both.
3. Change the **Start** to **7 days ago** and leave the **End** as **Today** (default).
4. Click **Apply**.
Financial year-to-date (most recent)
Suppose your financial year runs from April to March and you want to see this year's financial performance so far (September). Going forward, you want to see data for the financial year-to-date on any given day.
1. Select the **Month** period type.
2. Click **Use dynamic dates** at the bottom of both the **Start** and **End** calendars. By default, the **Relative** dynamic option is selected for both.
3. Select **Recent** > **Most recent** > **April** for the **Start**.
4. Leave **Relative** > **This month** (default) selected for the **End**.
5. Click **Apply**.
Yesterday (one of special dynamic dates for days)
In addition to the relative options, the Day period type has special rules you can use to set dynamic start and/or end dates:
* **First day**: Always the first day of the month.
* **Last day**: Always the last day of the month.
* **Match today**: The same day number as today. For example, the 29th of each month.
* **Match yesterday**: The same day number as yesterday. For example, the 28th of each month.
Suppose you want to quickly review the previous day's data on any given day.
1. Select the **Day** period type.
2. Click **Use dynamic dates** at the bottom of both the **Start** and **End** calendars. By default, the **Relative** dynamic option is selected for both.
3. Select **Special** > **Match yesterday** for both the **Start** and **End**.
4. Click **Apply**.
