API sometimes returns timestamp instead of date time string

Developer Support APIs & Integrations
1

For one of our customers using our marketplace integration, we noticed that the API behaves kind of strangly.

Normaly the API returns datetimes in the format “2025-02-26T09:30:57.465Z” and dates in the format “2025-02-26”.

For one date field the value returns is a timestamp in milliseconds 1740441600000.

Reported meta data for this field is type “date” and fieldType “calculation_equation”. So it seems that the API doesn’t convert the timestamp for calculated date fields.

It works though for “datetime” fields which have the fieldType “calculation_equation”.

We are using v3 API and in this case it was for Deals (Accounts Dashboard | HubSpot)

2

Hi @attrib! Thank you for this post. Date fields come in many formats depending on the property itself. Have you verified the property type and noticed any consistency with the response?

I want to invite some subject matter experts to see if they have any suggestions.

Hey @Anton, @Mike_Eastwood, @Bortami have you experienced this behavior with date values returned in varying formats?

Best,

Kennedy

3

Hi @attrib

In the API Properties Doc it says a `dateTime` can be returned as a Date Time (UTC) or a Unix Timestamp (which is always in milliseconds).

In one app I check “is integrer” to decide how to handle the returned property.

All part of the fun!

Mike

p.s. thank you for the mention @kennedyp

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4

Thanks for the reply and answer.

I just hoped that we either can identifiy fields doing it this way, using the meta data of the field. And not just guessing using is_int.

Also it looked stranged because most fields return a DateTime, just that one field…