objective c - NSDate not showing exact days passed -

i made small program calculate difference between 2 dates, , output number of days, , months passed. program shows number of months, , number of days fine, separately. however, when join them in flag, output shows right number of months, , "12" number of days, no matter date put in. i've tried inline components: (nsdaycalendarunit|nsmonthcalendarunit), same problem occurs. here code. help!

#import <foundation/foundation.h>  int main(int argc, const char * argv[]) {  @autoreleasepool {         nsdate *startdate=[nsdate datewithstring:@"2004-2-24 1:54:10 +0600"];         nsdate *today=[nsdate date];         nscalendar *gregorian = [[nscalendar alloc]initwithcalendaridentifier:nsgregoriancalendar];         nsuinteger flags = nsmonthcalendarunit | nsdaycalendarunit;         nsdatecomponents *components = [gregorian components: flags  fromdate:startdate todate:today options:0];         nsinteger days = [components day];         nsinteger months = [components month];         nslog(@"%li",(long)days);         nslog(@"%li",(long)months);       }     return 0; } 

output:

 2013-05-05 14:49:36.943 calendercalc[4111:303] 12  2013-05-05 14:49:36.944 calendercalc[4111:303] 110 

the output shows "12" number of days, no matter date put in.

are sure? when use startdate of @"2013-4-30 1:54:10 +0600", see days 6 , months 0. code looks fine.

edit

here's how compare 2 dates' "day of month", regardless of whether or not they're in same month or year.

nscalendar* gregorian = [[nscalendar alloc]initwithcalendaridentifier:nsgregoriancalendar] ; nsdate* startdate = [nsdate datewithstring:@"2013-4-18 1:54:10 +0600"] ; nsdate* today     = [nsdate datewithstring:@"2013-5-05 1:54:10 +0600"] ; nsdatecomponents* startdatecomponents = [gregorian components:nsdaycalendarunit fromdate:startdate] ; nsdatecomponents* todaycomponents     = [gregorian components:nsdaycalendarunit fromdate:today] ; int daysapart = fabs(startdatecomponents.day - todaycomponents.day) ;