iPhone: Convert date string to a relative time stamp

Question

I\'ve got a timestamp as a string like:

Thu, 21 May 09 19:10:09 -0700

and I\'d like to convert it to a relative time stamp like

Answer 1

My solution:

- (NSString *) dateToName:(NSDate*)dt withSec:(BOOL)sec {

    NSLocale *locale = [NSLocale currentLocale];
    NSTimeInterval tI = [[NSDate date] timeIntervalSinceDate:dt];
    if (tI < 60) {
      if (sec == NO) {
           return NSLocalizedString(@"Just Now", @"");
       }
       return [NSString stringWithFormat:
                 NSLocalizedString(@"%d seconds ago", @""),(int)tI];
     }
     if (tI < 3600) {
       return [NSString stringWithFormat:
                 NSLocalizedString(@"%d minutes ago", @""),(int)(tI/60)];
     }
     if (tI < 86400) {
      return [NSString stringWithFormat:
                 NSLocalizedString(@"%d hours ago", @""),(int)tI/3600];
     }

     NSDateFormatter *relativeDateFormatter = [[NSDateFormatter alloc] init];
     [relativeDateFormatter setTimeStyle:NSDateFormatterNoStyle];
     [relativeDateFormatter setDateStyle:NSDateFormatterMediumStyle];
     [relativeDateFormatter setDoesRelativeDateFormatting:YES];
     [relativeDateFormatter setLocale:locale];

     NSString * relativeFormattedString = 
            [relativeDateFormatter stringForObjectValue:dt];
     return relativeFormattedString;
}

Answer 2

In the interest of completeness, based on a @Gilean's answer, here's the complete code for a simple category on NSDate that mimics rails' nifty date helpers. For a refresher on categories, these are instance methods that you would call on NSDate objects. So, if I have an NSDate that represents yesterday, [myDate distanceOfTimeInWordsToNow] => "1 day".

Hope it's useful!

@interface NSDate (NSDate_Relativity)

-(NSString *)distanceOfTimeInWordsSinceDate:(NSDate *)aDate;
-(NSString *)distanceOfTimeInWordsToNow;

@end



@implementation NSDate (NSDate_Relativity)


-(NSString *)distanceOfTimeInWordsToNow {
    return [self distanceOfTimeInWordsSinceDate:[NSDate date]];

}

-(NSString *)distanceOfTimeInWordsSinceDate:(NSDate *)aDate {
    double interval = [self timeIntervalSinceDate:aDate];

    NSString *timeUnit;
    int timeValue;

    if (interval < 0) {
        interval = interval * -1;        
    }

    if (interval< 60) {
        return @"seconds";

    } else if (interval< 3600) { // minutes

        timeValue = round(interval / 60);

        if (timeValue == 1) {
            timeUnit = @"minute";

        } else {
            timeUnit = @"minutes";

        }


    } else if (interval< 86400) {
        timeValue = round(interval / 60 / 60);

        if (timeValue == 1) {
            timeUnit = @"hour";

        } else {
            timeUnit = @"hours";
        }


    } else if (interval< 2629743) {
        int days = round(interval / 60 / 60 / 24);

        if (days < 7) {

            timeValue = days;

            if (timeValue == 1) {
                timeUnit = @"day";
            } else {
                timeUnit = @"days";
            }

        } else if (days < 30) {
            int weeks = days / 7;

            timeValue = weeks;

            if (timeValue == 1) {
                timeUnit = @"week";
            } else {
                timeUnit = @"weeks";
            }


        } else if (days < 365) {

            int months = days / 30;
            timeValue = months;

            if (timeValue == 1) {
                timeUnit = @"month";
            } else {
                timeUnit = @"months";
            }

        } else if (days < 30000) { // this is roughly 82 years. After that, we'll say 'forever'
            int years = days / 365;
            timeValue = years;

            if (timeValue == 1) {
                timeUnit = @"year";
            } else {
                timeUnit = @"years";
            }

        } else {
            return @"forever ago";
        }
    }

    return [NSString stringWithFormat:@"%d %@", timeValue, timeUnit];

}

@end

Answer 3

In Swift

Usage:

let time = NSDate(timeIntervalSince1970: timestamp).timeIntervalSinceNow
let relativeTimeString = NSDate.relativeTimeInString(time)
println(relativeTimeString)

Extension:

extension NSDate {
    class func relativeTimeInString(value: NSTimeInterval) -> String {
        func getTimeData(value: NSTimeInterval) -> (count: Int, suffix: String) {
            let count = Int(floor(value))
            let suffix = count != 1 ? "s" : ""
            return (count: count, suffix: suffix)
        }

        let value = -value
        switch value {
            case 0...15: return "just now"

            case 0..<60:
                let timeData = getTimeData(value)
                return "\(timeData.count) second\(timeData.suffix) ago"

            case 0..<3600:
                let timeData = getTimeData(value/60)
                return "\(timeData.count) minute\(timeData.suffix) ago"

            case 0..<86400:
                let timeData = getTimeData(value/3600)
                return "\(timeData.count) hour\(timeData.suffix) ago"

            case 0..<604800:
                let timeData = getTimeData(value/86400)
                return "\(timeData.count) day\(timeData.suffix) ago"

            default:
                let timeData = getTimeData(value/604800)
                return "\(timeData.count) week\(timeData.suffix) ago"
        }
    }
}

Answer 4

I saw that there were several time ago functions in snippets of code on Stack Overflow and I wanted one that really gave the clearest sense of the time (since some action occurred). To me this means "time ago" style for short time intervals (5 min ago, 2 hours ago) and specific dates for longer time periods (April 15, 2011 instead of 2 years ago). Basically I thought Facebook did a really good job at this and I wanted to just go by their example (as I'm sure they out a lot of thought into this and it is very easy and clear to understand from the consumer perspective).

After a long time of googling I was pretty surprised to see that no one had implemented this as far as I could tell. Decided that I wanted it bad enough to spend the time writing and thought that I would share.

Hope you enjoy :)

Get the code here: https://github.com/nikilster/NSDate-Time-Ago

Answer 5

Not sure why this isnt in cocoa-touch, i nice standard way of doing this would be great.

Set up some types to keep the data in, it will make it easier if you ever ned to localise it a bit more. (obviously expand if you need more time periods)

typedef struct DayHours {
    int Days;
    double Hours;
} DayHours;


+ (DayHours) getHourBasedTimeInterval:(double) hourBased withHoursPerDay:(double) hpd
{
    int NumberOfDays = (int)(fabs(hourBased) / hpd);
    float hoursegment = fabs(hourBased) - (NumberOfDays * hpd);
    DayHours dh;
    dh.Days = NumberOfDays;
    dh.Hours = hoursegment;
    return dh;
}

NOTE: I"m using an hour based calculation , as that is what my data is in. NSTimeInterval is second based. I also had to convert between the two.