Simple RelativeDate utility class for displaying dates relative to now. [date relativeString] == 3 days ago, 24 years from now, 2 seconds ago, etc.

NSDate+RelativeDate.h

//
//  NSDate+RelativeDate.h
//  RWRelativeDate
//
//  Created by Robert White on 19/09/2013.
//

#import <Foundation/Foundation.h>

@interface NSDate (RelativeDate)

- (NSString *)relativeString;

@end

NSDate+RelativeDate.m

//
//  NSDate+RelativeDate.m
//  RWRelativeDate
//
//  Created by Robert White on 19/09/2013.
//

#import "NSDate+RelativeDate.h"

@implementation NSDate (RelativeDate)

- (NSString *)relativeString
{
    NSTimeInterval timeInterval =  [self timeIntervalSinceNow];
    
    NSString *relativity;
    
    if (timeInterval < 0) {
        relativity = @"ago";
        timeInterval = timeInterval * -1;
    } else {
        relativity = @"from now";
    }
    
    NSInteger time;
    NSString *unit;

    if (timeInterval <= 60) {
        time = floor(timeInterval);
        unit = @"second";
    } else if (timeInterval <= 3600) {
        time = floor(timeInterval / 60);
        unit = @"minute";
    } else if (timeInterval <= 86400) {
        time = floor(timeInterval / 3600);
        unit = @"hour";
    } else if (timeInterval <= 604800) {
        time = floor(timeInterval / 86400);
        unit = @"day";
    } else if (timeInterval <= 2419200) {
        time = floor(timeInterval / 604800);
        unit = @"week";
    } else if (timeInterval <= 31557600) {
        time = floor(timeInterval / 2419200);
        unit = @"month";
    } else if (timeInterval <= [[NSDate distantFuture] timeIntervalSinceNow]){
        time = floor(timeInterval / 31557600);
        unit = @"year";
    } else {
        return [NSString stringWithFormat: @"a long, long time %@...", relativity];
    }

    if (time > 1) unit = [NSString stringWithFormat:@"%@s", unit];
    
    return [NSString stringWithFormat:@"%d %@ %@", time, unit, relativity];
}

@end