NSDate category to make easy to work with date components

NSDate+Utilities.h

//
//  NSDate+Utilities.h
//
//  Created by PEDRO MUÑOZ CABRERA on 15/03/13.
//  Copyright (c) 2013. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSDate (Utilities)

@property (nonatomic, readonly) NSInteger year;
@property (nonatomic, readonly) NSInteger month;
@property (nonatomic, readonly) NSInteger day;
@property (nonatomic, readonly) NSInteger hour;
@property (nonatomic, readonly) NSInteger minute;
@property (nonatomic, readonly) NSInteger second;


+ (NSDate *)dateFromString:(NSString *)dateStr usingFormat:(NSString *)format;

+ (NSDate *)justTimeFromString:(NSString *)dateStr usingFormat:(NSString *)format;

+ (BOOL)date:(NSDate*)date isBetweenDate1:(NSDate *)date1 andDate2:(NSDate *)date2;

+ (NSString *)timeStrFromTimeInterval:(NSTimeInterval)timeInterval;

+ (NSString *)timeStrDiferenceFromTimeInterval:(NSTimeInterval)timeInterval1  andTimeInterval2:(NSTimeInterval)timeInterval2;
  
- (NSInteger) week;

- (NSInteger) weekday;

- (NSString*) monthName;

- (NSDate *)dateFromString:(NSString *)dateStr usingFormat:(NSString *)format;

- (NSString *)toStringUsingFormat:(NSString *)format;

- (NSDate *)dateByAddingDay:(NSInteger)day;

- (NSDate *)justTime;

- (NSDate *)justDate;

// Retrieving intervals
- (NSInteger) minutesAfterDate: (NSDate *) aDate;
- (NSInteger) minutesBeforeDate: (NSDate *) aDate;
- (NSInteger) hoursAfterDate: (NSDate *) aDate;
- (NSInteger) hoursBeforeDate: (NSDate *) aDate;
- (NSInteger) daysAfterDate: (NSDate *) aDate;
- (NSInteger) daysBeforeDate: (NSDate *) aDate;
- (NSInteger)distanceInDaysToDate:(NSDate *)anotherDate;  



    


@end

NSDate+Utilities.m

//
//  NSDate+Utilities.m
//
//  Created by PEDRO MUÑOZ CABRERA on 15/03/13.
//  Copyright (c) 2013. All rights reserved.
//

#import "NSDate+Utilities.h"

#define kDefFormat @"dd-MM-yyyyy hh:mm"

#define D_MINUTE	60
#define D_HOUR		3600
#define D_DAY		86400
#define D_WEEK		604800
#define D_YEAR		31556926

@interface NSDate(private)
- (NSDateComponents *)components:(NSUInteger)components;
@end

@implementation NSDate (Utilities)

- (NSInteger)year {
    return [self components:NSYearCalendarUnit].year;
}

- (NSInteger)month {
    return [self components:NSMonthCalendarUnit].month;
}

- (NSInteger)day {
    return [self components:NSDayCalendarUnit].day;
}

- (NSInteger)hour {
    return [self components:NSHourCalendarUnit].hour;
}

- (NSInteger)minute {
    return [self components:NSMinuteCalendarUnit].minute;
}

- (NSInteger)second {
    return [self components:NSSecondCalendarUnit].second;
}

- (NSInteger) week
{
  return [self components:NSWeekdayCalendarUnit].week;
}

- (NSInteger) weekday
{
	return [self components:NSWeekdayOrdinalCalendarUnit].weekday;
}

- (NSString*) monthName {
    
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"MMMM"];
    [formatter setLocale:[NSLocale currentLocale]];
    
    NSString *stringFromDate = [formatter stringFromDate:self];
    
    return stringFromDate;
}

- (NSDate *)dateFromString:(NSString *)dateStr usingFormat:(NSString *)format {
    NSDateFormatter *df = [[NSDateFormatter alloc] init];
    NSTimeZone *gmt = [NSTimeZone timeZoneWithAbbreviation:@"GMT"];
    [df setTimeZone:gmt];
    [df setDateFormat:format];
    
    return [df dateFromString:dateStr];
}

+ (NSDate *)dateFromString:(NSString *)dateStr usingFormat:(NSString *)format {
    NSDateFormatter *df = [[NSDateFormatter alloc] init];
    NSTimeZone *gmt = [NSTimeZone timeZoneWithAbbreviation:@"GMT"];
    [df setTimeZone:gmt];
    [df setDateFormat:format];
    
    return [df dateFromString:dateStr];
}

- (NSString *)toStringUsingFormat:(NSString *)format {
    NSDateFormatter *df = [[NSDateFormatter alloc] init];
    NSTimeZone *gmt = [NSTimeZone timeZoneWithAbbreviation:@"GMT"];
    [df setTimeZone:gmt];
    [df setDateFormat:format];
    return [df stringFromDate:self];
}


- (NSDate *)dateByAddingDay:(NSInteger)day {
    return [NSDate date:self byAddingDay:day];
}

- (NSDate *)justTime{
//
//        NSDateComponents *dc = [[NSDateComponents alloc] init];
//        [dc setYear:0];
//        [dc setMonth:0];
//        [dc setDay:0];
//        NSDate *dateModified = [[NSCalendar currentCalendar] dateByAddingComponents:dc toDate:self options:0];
//        
//        return dateModified;
    
    unsigned int flags = NSHourCalendarUnit | NSMinuteCalendarUnit;
    NSCalendar* calendar = [NSCalendar currentCalendar];
    NSDateComponents* components = [calendar components:flags fromDate:self];
    return [calendar dateFromComponents:components];

}

- (NSDate *)justDate{
    
    NSCalendar *cal = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateComponents* comps = [cal components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit fromDate:self];
    [cal setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
    return [cal dateFromComponents:comps];
}

+ (NSDate *)date:(NSDate *)date
    byAddingYear:(NSInteger)year
           month:(NSInteger)month
             day:(NSInteger)day
            hour:(NSInteger)hour
          minute:(NSInteger)minute
          second:(NSInteger)second {
    
    NSDateComponents *dc = [[NSDateComponents alloc] init];
    
    dc.year = year;
    dc.month = month;
    dc.day = day;
    dc.hour = hour;
    dc.minute = minute;
    dc.second = second;
    
    NSCalendar *c = [NSCalendar currentCalendar];
    
    return [c dateByAddingComponents:dc
                              toDate:date
                             options:0];
    
}

+ (NSDate *)date:(NSDate *)date byAddingDay:(NSInteger)day {
    
    return [NSDate date:date
           byAddingYear:0
                  month:0
                    day:day
                   hour:0
                 minute:0
                 second:0];
    
}

+ (NSDate *)justTimeFromString:(NSString *)dateStr usingFormat:(NSString *)format{
    
    NSDate *fecha = [NSDate dateFromString:dateStr usingFormat:format];
    NSString *timeStr = [fecha toStringUsingFormat:@"HH:mm"];
    return  [NSDate dateFromString:timeStr usingFormat:@"HH:mm"];
}

+ (BOOL)date:(NSDate*)date isBetweenDate1:(NSDate *)date1 andDate2:(NSDate *)date2{
    
    if ((([date compare: date1] == NSOrderedDescending) || ([date compare: date1] == NSOrderedSame))
        && (([date compare: date2] == NSOrderedAscending) || ([date compare: date2] == NSOrderedSame))) {
        return YES;
    }
    
    return NO;
}


- (NSDateComponents *)allComponents {
    return [self components:
            NSYearCalendarUnit |
            NSMonthCalendarUnit |
            NSDayCalendarUnit |
            NSWeekCalendarUnit |
            NSHourCalendarUnit |
            NSMinuteCalendarUnit |
            NSSecondCalendarUnit |
            NSWeekdayCalendarUnit |
            NSWeekdayOrdinalCalendarUnit];
}


+ (NSString *)timeStrFromTimeInterval:(NSTimeInterval)timeInterval{
    
   NSDate *date = [[NSDate  alloc] initWithTimeIntervalSince1970: timeInterval];
    NSString *timeStr = [date toStringUsingFormat:@"HH:mm"];
    
    return timeStr;
}


+ (NSString *)timeStrDiferenceFromTimeInterval:(NSTimeInterval)timeInterval1  andTimeInterval2:(NSTimeInterval)timeInterval2{
    
    NSTimeInterval tsDiff = timeInterval1 - timeInterval2;
    
    // Divide the interval by 3600 and keep the quotient and remainder
    div_t h = div(tsDiff, 3600);
    int hours = h.quot;
    // Divide the remainder by 60; the quotient is minutes, the remainder
    // is seconds.
    div_t m = div(h.rem, 60);
    int minutes = m.quot;

    NSString *timeStr =[NSString stringWithFormat:@"%dh %dm", hours, minutes];
    
    
    return timeStr;
}


#pragma mark Retrieving Intervals

- (NSInteger) minutesAfterDate: (NSDate *) aDate
{
	NSTimeInterval ti = [self timeIntervalSinceDate:aDate];
	return (NSInteger) (ti / D_MINUTE);
}

- (NSInteger) minutesBeforeDate: (NSDate *) aDate
{
	NSTimeInterval ti = [aDate timeIntervalSinceDate:self];
	return (NSInteger) (ti / D_MINUTE);
}

- (NSInteger) hoursAfterDate: (NSDate *) aDate
{
	NSTimeInterval ti = [self timeIntervalSinceDate:aDate];
	return (NSInteger) (ti / D_HOUR);
}

- (NSInteger) hoursBeforeDate: (NSDate *) aDate
{
	NSTimeInterval ti = [aDate timeIntervalSinceDate:self];
	return (NSInteger) (ti / D_HOUR);
}

- (NSInteger) daysAfterDate: (NSDate *) aDate
{
	NSTimeInterval ti = [self timeIntervalSinceDate:aDate];
	return (NSInteger) (ti / D_DAY);
}

- (NSInteger) daysBeforeDate: (NSDate *) aDate
{
	NSTimeInterval ti = [aDate timeIntervalSinceDate:self];
	return (NSInteger) (ti / D_DAY);
}

- (NSInteger)distanceInDaysToDate:(NSDate *)anotherDate
{
    NSCalendar *gregorianCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateComponents *components = [gregorianCalendar components:NSDayCalendarUnit fromDate:self toDate:anotherDate options:0];
    return components.day;
}


#pragma mark - Private

- (NSDateComponents *)components:(NSUInteger)components {
    return [[NSCalendar currentCalendar] components:components
                                           fromDate:self];
}




@end

Pillado ;)

Gracias Pedro

Add new methods to make easier to convert DateTime to Fuzzy Time