gistfile1.m

#import <Foundation/Foundation.h>
#define SECOND_INTERVAL 1
#define MINUTE_INTERVAL (SECOND_INTERVAL * 60)
#define HOUR_INTERVAL (MINUTE_INTERVAL * 60)
#define DAY_INTERVAL (HOUR_INTERVAL * 24)
#define WEEK_INTERVAL (DAY_INTERVAL * 7)

int main(int argc, char *argv[]) {
    NSAutoreleasePool *p = [[NSAutoreleasePool alloc] init];

    NSDate *now = [NSDate date];
    NSInteger time = (NSInteger)[now timeIntervalSinceReferenceDate];

    NSInteger mod = time % DAY_INTERVAL;
    NSInteger expectedValue = (NSInteger)[now timeIntervalSinceReferenceDate];

    while (expectedValue - DAY_INTERVAL >= 0)
        expectedValue -= DAY_INTERVAL;

    NSLog(@"Day: %d", DAY_INTERVAL);
    NSLog(@"Time: %d", time);
    NSLog(@"Modded value: %d", mod);
    NSLog(@"Loopy value: %d", expectedValue);
    NSLog(@"Is this right? %@", expectedValue == mod ? @"Why yes, yes it is..." : @"Nope, magic C things are breaking!");
    [p release];
}