Segments with Date Criteria

Hi,

I'm trying to build segments with a date condition.

We have a user attribute that's a date in the format YYYY-MM-DD, but I'm getting zero matches regardless of the date condition. I can see the dates are in there based on the suggestions in the Pinpoint UI, but they must not be suitable for the Before/After matching.

I presume I've misunderstood - either we can't target based on a user attribute that's a date or YYYY-MM-DD isn't the correct format to pass into the API. Please can someone point out where I've gone wrong?

Thanks,
Mike