AppleScript returns error on defining date
Try:

set dateString to "Tuesday, April 12, 2016 at 12:00:00 AM"
set dateReference to date dateString

tell current application
    -- insert commands here
end tell


Another approach:

set y to 2001
set m to 6
set d to 12
set h to 12
set min to 12
set s to 12

set cd to current date
tell cd
    set its year to y
    set its month to m
    set its day to d
    set its hours to h
    set its minutes to min
    set its seconds to s
end tell