In addition to hrnxm comments, typically in Elm you can have a reasonable precise date/time value by having a “subscription” (see Commands and Subscriptions · An Introduction to Elm) that runs periodically and ask the system for current date/time.
That way, you store the value in your Model.currentDate and use wherever you want in your app. Also, to avoid having to deal with Maybe's you can have a init value passed from JS (see reply above).