How to use compare dates in SharePoint 2013 REST search api?

I have a rest URL that uses Search API, for SP2013. I can use regular filters

    "/_api/search/query?querytext='contenttype:News Item'

like this says, get all items with content type is `news item`, but now I have a date type managed property, how can I set it so that I filter on if the date field is <= current date. Is there something like

    "/_api/search/query?querytext='articleDate le [today]'

I can replace [today] with an ISO converted string representation of the current date in javascript, so I just put that for simplicity.

But does anyone know how to compare dates in search rest query?

Thanks