That wouldn’t coerce for me (even without the typo), but this does. This should return the number of days.
set dayLate to round (((current date) - (date "1/15/2003")) / (60 * 60 * 24))
-- Delete the following after testing --
if dayLate is 1 then
display dialog "You are " & dayLate & " day late!" buttons {"Not Bad"} default button 1
end if
if dayLate is greater than 1 then
display dialog "You are " & dayLate & " days late!" buttons {"Yikes!"} default button 1
end if
if dayLate is 0 then
display dialog "You aren't late!" buttons {"Excellent!"} default button 1
end if
set theDate to date "01/15/2003"
set dayLate to round (((current date) - (theDate)) / (60 * 60 * 24))
So does this:
set dd to display dialog "Enter a date:" default answer "01/15/2003"
set theDate to date (text returned of dd)
set dayLate to round (((current date) - (theDate)) / (60 * 60 * 24))
display dialog "" & dayLate & " days late."