Date is too short

I'm using Elasticsearch with ruby. I have a Date field that is a Datetime converted to "iso8601" on the format "2018-07-29T13:00:00Z" . the field is formatted as a date_time_no_millis

attribute :starts_at, Date, mapping: { format: "date_time_no_millis" }

The problem is I'm getting date is too short, any suggestions

Elasticsearch::Transport::Transport::Errors::BadRequest: [400] {"error":{"root_cause":[{"type":"mapper_parsing_exception","reason":"failed to parse [starts_at]"}],"type":"mapper_parsing_exception","reason":"failed to parse [starts_at]","caused_by":{"type":"illegal_argument_exception","reason":"Invalid format: "2018-07-29" is too short"}},"status":400}

It's easier for us to help if you keep the question to one thread :slight_smile: