Your masterCalendar.Date and your calls.Date have different internal formats, so they will not link. masterCalendar.Date are integers, calls.Date have decimal (time values).
date() is a formatting function. It only affects the display value, not the internal vaue.
When you extract Date from caDateTime you should do it like this:
date(floor(caDateTime)) as [Date
That will extract the integer (date) portion.