My calculation field (Countdown) is this and it gives a negative number (set to Integer)
if(#{startdate}!=0,ceil((#{startdate}-now())/86400),0)
then in a javascript field (Days to Go) I have this
if (field("Countdown")<="0")'0 Days\nHappy Holidays';
else if (field("Countdown") =="1") '1 Day to go';
else field("Countdown") +' Days to go'