Hi,
We have migrated our contact list from another ESP to Klaviyo. We have included a custom property Birthday and mapped it as a “date” format.
Currently I’m seeing this in our account:
- Imported contacts include date written as
Before migrating we have formatted Birthday dates as MM/DD/YYYY as seen below.
Our pop-up form collecting birthdays is using the same profile property “Birthday” and date data type formatted as MM/DD/YYYY.
We wish to know if this is a common and correct way for our data to be displayed on a profile or do we have to re-import our Birthday data field from the primary exported list and change formatting in the mentioned corresponding pop-up and preferences page setup?
I would also like to clarify why the source property in imported contacts is set as “-6”?
If we do have to re-import Birthday data to the account, will it automatically update only the existing Birthday property assigned to a specific e-mail?
Thank you,
Birthday property date formatting
Best answer by retention
Hi
So Klaviyo can recognize a few date formats so that it will properly work with your Segmentation rules and any date triggered Flows.
You can see the documentation of acceptable date formats here:
- Understanding data types : Date
- Acceptable date and timestamp formats for profile and event properties
As for the “-6” source value - if you don’t provide a $source value, then Klaviyo will set one for you according to the general source table here:
When profiles get added to Klaviyo, you can specify the Source value so you can differentiate them a Lists Growth Report.

Commonly, this is done via the Klaviyo Signup Form where you can define the source value, but it also applies to any external email capture tools and/or via the API.
See this example:

However, if none is given, or if it’s added via a known Partner integration, the source value will default to one of those values.
A “-6” just means the Profile was created via a “Manually initiated” method (e.g. You uploaded the email manually).
Hope that helps!
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