Notion users often need to track events or deadlines that depend on data from another database. A relation property links two databases, but calendar views require a date property to display items on the timeline. By default, a relation property does not carry date values from the related database. You can use a rollup property to pull a date from the related database and then display that date in a calendar view. This article explains how to set up a relation, create a rollup for a date field, and configure a calendar view to show aggregated dates.
Key Takeaways: Setting Up a Relation for Calendar Date Aggregation
- Relation property in Database A > Database B: Links two databases so you can refer to records in the second database.
- Rollup property with Date value: Pulls a date property from the related database into the primary database for calendar display.
- Calendar view + Rollup date filter: Shows only items with a valid rolled-up date; hides items without a date to keep the view clean.
How the Relation and Rollup Properties Work Together for Calendar Views
A relation property creates a link between two databases. For example, you might have a Projects database and a Milestones database. Each project can relate to multiple milestones. A calendar view in Notion requires a date property to place items on the timeline. Because a relation property does not contain a date, you cannot directly use it in a calendar view. The solution is a rollup property that reads a date from the related database and brings it into the primary database. Once the rollup property contains a date, you can configure a calendar view to use that rolled-up date as the display date. This setup allows you to aggregate and visualize dates from related records without duplicating data.
Prerequisites: You need two databases with at least one common field. The related database must contain a date property. You also need edit permissions on both databases.
Steps to Add a Relation and Rollup Date for Calendar Aggregation
- Create the relation property in the primary database
Open the primary database (the one where you want the calendar view). Click the + icon in the last column header. Select Relation. In the dialog, choose the related database. Name the relation, for example “Milestone.” Notion creates a relation column and a corresponding relation column in the related database. - Link records between the two databases
Click into any cell in the new relation column. A dropdown shows records from the related database. Select one or more records to link. For calendar aggregation, each primary record should link to at least one related record that has a date property filled in. - Add a rollup property to pull the date
Click the + icon again. Select Rollup. Name it “Milestone Date.” In the rollup configuration, set the Relation to the relation you just created (for example, “Milestone”). Set the Property to the date property in the related database (for example, “Due Date”). Set the Calculate option to one of the following: Show Original (if you want a single date), Earliest Date, Latest Date, or Date Range. For a single date in a calendar view, choose Earliest Date or Latest Date. Click Save. - Create a calendar view in the primary database
Click the + Add a View button at the top left of the database. Select Calendar. Name the view, for example “Milestone Calendar.” In the calendar view settings, click the Date field dropdown. Select the rollup property you created, for example “Milestone Date.” Notion now places each record on the calendar based on the rolled-up date. - Filter out records without a date
In the calendar view, click the Filter button. Add a filter: Milestone Date is not empty. This hides records that have no linked milestone or no date in the related record. The calendar view shows only items that have a valid aggregated date.
Common Mistakes and Limitations When Using Rollup Dates in Calendar Views
Rollup date shows blank or no value
If the rollup property appears empty in the primary database, the related record either has no date property filled or the relation is not properly linked. Verify that the related database contains a date property with a value. Also confirm that the relation column in the primary database has at least one linked record.
Calendar view shows duplicate items or incorrect dates
When a primary record relates to multiple related records, the rollup with Earliest Date or Latest Date picks a single date. If you select Show Original, Notion may not display the item if multiple values exist. Use Earliest Date or Latest Date to get a single date. If you need to show each related date separately, create a linked database view inside the record instead of using a rollup.
Rollup date cannot be edited directly in the calendar view
The rollup property is read-only. To change the date, you must edit the date property in the related database. Open the related record and update the date there. The rollup will update automatically in the primary database.
Relation + Rollup vs Manual Date Copy: Workflow Comparison
| Feature | Relation + Rollup Date | Manual Date Copy |
|---|---|---|
| Data duplication | No duplication; date stays in one place | Date is copied into each primary record |
| Update syncing | Automatic; changes in related database reflect immediately | Manual; you must update each copy |
| Calendar view readiness | Requires rollup setup; works with any date property | Direct; date property is already in the primary database |
| Editing convenience | Must edit in related database | Edit directly in the primary database |
You can now link two databases and display aggregated dates in a calendar view without copying data. Use the filter to hide records without dates for a clean timeline. For complex schedules with multiple milestones per project, experiment with the Date Range rollup to show start and end dates directly on the calendar.