> For the complete documentation index, see [llms.txt](https://help.tellius.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.tellius.com/settings/preferences/calendar-settings.md).
# Calendar Settings
Under **Settings → Appearance & Preferences → Preferences → Calendar Settings**, admins can manage custom, fiscal, and retail calendars used for analytics and filters. Many organizations don't report on a standard January-to-December year, so a custom calendar lets Tellius group and compare data using your own reporting periods instead.
#### The Calendars list
The page lists every calendar defined in the environment. Each entry shows the calendar's name and its description. The calendar currently set as the default is marked with a **Default** label.
Use the **Search** box to filter the list by name, which helps once many calendars exist.
Each calendar row has three controls:
* **Preview** (magnifier icon): Opens a preview of the generated calendar as a table, with one row per day. Columns include the date and the calendar's derived time fields, such as *FY Week, FY Month, FY Quarter, FY Weekday,* and *FY Year*. The preview is paginated and shows the total number of rows generated, so you can confirm the calendar looks correct before using it.
* **Download** (download icon): Downloads the calendar as a CSV file.
* **More actions** (three-dot menu): Opens a menu with **Edit**, **Set as Default**, and **Delete**.
* **Edit** reopens the calendar's settings so you can change them.
* **Set as Default** makes this the default calendar for the environment. Click Confirm in the confirmation window to proceed.
* **Delete** removes the calendar.
### Add a custom calendar
Click **Add Custom Calendar** to open a menu with four calendar types:
* **Standard (ISO)**
* **Fiscal**
* **Retail**
* **Import from CSV**
Each type opens its own form. All four share the same buttons at the bottom: **Cancel** to discard, **Preview** to see the calendar layout before applying, and **Save changes** to create it.
#### **Standard (ISO)**
Creates a calendar using custom periods and offsets. The form has these fields:
* **Name** *(required)*: A name for the calendar.
* **Description** *(required)*: A short description.
* **Start month and year**: The month and year the calendar begins.
* **First Day of the Week**: The day each week starts on, chosen from a dropdown.
* **End year**: The last year the calendar covers.
#### **Fiscal**
Creates a calendar aligned to your organization's fiscal reporting cycles. The form has these fields:
* **Name** *(required)* and **Description** *(required)*.
* **Start Date**: The date the fiscal calendar begins.
* **Fiscal Year Start Week Label Prefix** *(required)*: The prefix used when labeling weeks.
* **Fiscal Year Start Month Label Prefix** *(required)*: The prefix used when labeling months.
* **Fiscal Year Start Quarter Label Prefix** *(required)*: The prefix used when labeling quarters.
* **Days in Week** *(required)*: The number of days in each week.
* **Weeks in Month** *(required)*: The number of weeks in each month.
* **Weeks in Quarter** *(required)*: The number of weeks in each quarter.
* **Weeks in Year** *(required)*: The number of weeks in each year.
The label prefix fields control how periods are named in your results, and the four count fields define the length of each period. Together they let you reproduce a fiscal structure that doesn't follow the standard calendar.
#### **Retail**
Creates a retail calendar using a 4-4-5, 4-5-4, or 5-4-4 week distribution pattern. The form has these fields:
* **Name** *(required)* and **Description** *(optional)*.
* **Pattern Type** *(required)*: The week distribution pattern across the months in each quarter. 4-4-5 means the quarter's three months contain 4 weeks, 4 weeks, and 5 weeks. The available options are **4-4-5**, **4-5-4**, and **5-4-4**.
* **Week Start Day** *(required)*: The day each week starts on (for example, Sunday).
* **Fiscal Year Start Month** *(required)*: The month the fiscal year begins (for example, February).
* **Start Year** *(required)* and **End Year** *(required)*: The range of years the calendar covers.
#### **Import from CSV**
Creates a calendar from a file you upload, which is useful when your calendar is maintained outside Tellius. Use the same column layout as the calendar export, with one row per day, so exporting an existing calendar first gives you a working template.
* **Name** *(required)*: A name for the calendar.
* **Description (optional)**: A short description.
* **CSV file** *(required)*: Drag and drop your calendar CSV into the upload area, or click to browse and select it.
### When to choose which calendar
**Standard (ISO):** the closest to a normal calendar. You only set a start month/year, an end year, and which day the week starts on. Weeks and months fall where they naturally fall. Choose this when your reporting follows the regular calendar and you just need control over the week's start day or the year range.
**Fiscal:** you define the period structure yourself. It asks for days in a week, weeks in a month, weeks in a quarter, weeks in a year, plus label prefixes for weeks/months/quarters. Choose this when your organization's financial year doesn't match the standard calendar and you need periods built to your own definition. For example, a fiscal year starting in April with custom period lengths.
**Retail:** a preset structure rather than a hand-built one. You pick a 4-4-5, 4-5-4, or 5-4-4 pattern, a week start day, the fiscal year start month, and a year range. Each quarter is then 13 weeks split across three months per that pattern. Choose this when you're in retail or any business that compares like-for-like weeks, where every quarter needs the same number of weeks so week-over-week and year-over-year comparisons line up cleanly.
{% hint style="info" %}
Choose **Standard** if the regular calendar works, **Retail** if a standard 4-4-5-style pattern fits your business, **Fiscal** if neither does and you need to define the periods yourself.
{% endhint %}
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