Grab a date from the calendar?

Grab a date from the calendar?

When someone clicks on a date in a calendar view to add a new record is there a way to grab the date and pre-fill the appropriate field on the form. 
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On a week view is it possible to use a separate field for the time slots. For example I have a form to make appointments. The user first chooses a date and then chooses the time from a drop down list that only shows times in 1/2 hour increments. I cant use a date/time field because I don't want the user to be able choose times other than every 1/2 hour . 



Herb Wexler