检查日期是否为同一日历日

NSCalendar让你应对人日。所以你可以实现一个类似这样的类别:

@implementation NSDate (IsItToday)
- (BOOL)isToday {
    NSUInteger desiredComponents = NSEraCalendarUnit|NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit;
    NSDateComponents *myCalendarDate = [[NSCalendar currentCalendar] components:desiredComponents fromDate:self];
    NSDateComponents *today = [[NSCalendar currentCalendar] components:desiredComponents fromDate:[NSDate date]];
    return [myCalendarDate isEqual:today];
}
@end

你应该好好读一读这本书 Dates and Times Programming Topics for Cocoa

NSDate *today = [NSDate date];
NSTimeInterval difference = [today timeIntervalSinceDate:otherDate];
NSTimeInterval secondsPerDay = 24 * 60 * 60;
if (difference < secondsPerDay)
{
   //same day as today
}