It appears the date picker doesn't work in Version: 1.7.0 beta Build 14407. Several places I have tried but get no pop-up widget to choose the date...
1.) Creating a new patient (birthdate)
2.) Updating the patient birthdate on the Edit this Patient and Edit this Patient (Short Form) under dashboard demographics.
3.) Adding/Updating Person Attributes of date types on the Edit this Patient screen.
4.) Encounter Date - when creating a new encounter under Administration.
5.) Observation Date - when manually adding a new observation when viewing an encounter.
6.) Date fields on HTML forms using the HTML Data Entry Module.
7.) Date on patient dashboard when exiting patient from care.
My test systems have HTML Widgets module version 1.5.4, and it is started/running.