To filter events where a custom event property (e.g., a date property) is before a certain date in the Mixpanel UI, you should:
1. Format the date threshold as an ISO-formatted string:
YYYY-MM-DDTHH:MM:SS in UTC. For example: 2023-12-31T00:00:00.
2. Apply the filter in your report by selecting your custom date property and using the "is before" or "<" operator, then entering your threshold date in the ISO format above.
Mixpanel expects date properties to be in ISO format and in UTC. When you use the UI to filter by date, ensure you enter the date in this format for accurate filtering. For example, to filter for events where "Account Created Date" is before January 1, 2024, you would use:
```
Account Created Date < 2024-01-01T00:00:00
LBKSThis approach applies to both built-in and custom event properties of type "Date" in Mixpanel reports. If you are sending date properties to Mixpanel, always use the ISO format in UTC to ensure correct behavior in filters and reports <https://docs.mixpanel.com/docs/data-structure/property-reference/data-type#overview|Supported Properties Data Type> [Manage Timezones for Projects](https://docs.mixpanel.com/docs/orgs-and-projects/managing-projects#manage-timezones-for-projects).
If you are using the API or JQL, you would use the same ISO format for date comparisons. The Mixpanel UI will interpret the date according to your project’s timezone setting, but the underlying value should always be in UTC ISO format.
