HubSpot

Date fields

Using API v3, For a date only field, you need to explicitly set the date to midnight UTC

Function ScriptedField
  ScriptedField=FormatDate("@@ORG:date_entered@@", "yyyy-MM-ddT00:00:00Z")
End Function

Updating Contacts

When updating contacts, if you are matching on email address, you must be sure NOT to pass in a blank email address. HubSpot will not know which contact to update and will update a random contact with incorrect data.