var USER_ID = "12148"; var USER_SIGNUP_DATE = "2020-01-02T21:07:03Z"; mixpanel.people.set({ "$email": "jsmith@example.com", // only reserved properties need the $ "Sign up date": USER_SIGNUP_DATE, // Send dates in ISO timestamp format (e.g. "2020-01-02T21:07:03Z") "USER_ID": USER_ID, // use human-readable names "credits": 150 // ...or numbers });