IOS-string converted to nsdate type calculation is different from the current time by the number of days in a month

Nsstring * datestr = [DIC
Objectforkey: @ "date"]; // 2012-05-17 11:23:23

Nscalendar * Gregorian = [[nscalendar
Alloc]
Initwithcalendaridentifier: nsgregoriancalendar];

Nsuinteger unitflags =
Nsmonthcalendarunit | nsdaycalendarunit;

Nsdateformatter * format = [[nsdateformatter
Alloc]
Init];

[Format
Setdateformat: @ "yyyy-mm-dd hh: mm: SS"];

Nsdate * fromdate = [format datefromstring: datestr];

Nstimezone * fromzone = [nstimezone
Systemtimezone];

Nsinteger frominterval = [fromzone secondsfromgmtfordate: fromdate];

Nsdate * fromdate = [fromdate datebyaddingtimeinterval: frominterval];

Nslog (@ "fromdate = % @", fromdate );

[Format
Release];

Nsdate * Date = [nsdate
DATE];

Nstimezone * zone = [nstimezone
Systemtimezone];

Nsinteger interval = [zone secondsfromgmtfordate: date];

Nsdate * localedate = [date datebyaddingtimeinterval: interval];

Nslog (@ "enddate = % @", localedate );

Nsdatecomponents * components = [Gregorian components: unitflags
Fromdate: fromdate
Todate: localedate options: 0];

Nsinteger months = [components month];

Nsinteger days = [components Day]; // year [components year]

Nslog (@ "month = % d", months );

Nslog (@ "days = % d", days );

[Gregorian
Release];

If (months = 0 & days = 0 ){

Datestr = [[datestr
Substringfromindex: 11] substringtoindex: 5];

Cell. textlabel. Text = [nsstring
Stringwithformat: @ "today % @", datestr]; // Today

} Else
If (months = 0 & days = 1 ){

Datestr = [[datestr
Substringfromindex: 11] substringtoindex: 5];

Cell. textlabel. Text = [nsstring
Stringwithformat: @ "Yesterday % @", datestr]; // Yesterday

} Else {

Datestr = [datestr
Substringtoindex: 10];

Cell. textlabel. Text = datestr;

}