Getting human readable relative times and dates from a unix timestamp?

Question

Starting with a unix timestamp like 1290529723, how would I (assuming gmt) get the information on whether it is:

• today (if so, what time)

• in the last seven days (if so, which day ... mon, tues etc?)

• older than a week (if so, how to output in dd/mm/yy format?)

I need this for a list of messages like the iPhone's Mail app, where date/times are shown relative to the current date and time, like so:

15:45
Yesterday
Sunday
Saturday
10/10/10

etc

 

Answer 1

It takes a bit of fiddling to get a solution that respects the device's locale. The following method relativeStringFromDate returns a string representing the date, formatted as following:

• just the time if the date is today, according to locale (e.g. '3:40PM' or '15:40')
• 'Yesterday' if the date is yesterday (but will be internationalized into locale's language)
• name of the day of the week if date is two to six days ago (e.g. 'Monday', 'Tuesday', etc, again according to locale's language)

• just the date component if the date is over one week ago, according to locale (e.g. '1/20/2012' in US vs '20/1/2012' in Europe)

  - (NSString *)relativeStringFromDate:(NSDate *)date {
      if ([self dateIsToday:date])
          return [self dateAsStringTime:date];
      else if ([self dateIsYesterday:date])
          return [self dateAsStringDate:date];
      else if ([self dateIsTwoToSixDaysAgo:date])
          return [self dateAsStringDay:date];
      else
          return [self dateAsStringDate:date];
  }
  
  - (BOOL)date:(NSDate *)date 
          isDayWithTimeIntervalSinceNow:(NSTimeInterval)interval {
      NSDateFormatter *df = [[NSDateFormatter alloc] init];
      [df setDateFormat:@"yyyy-MM-dd"];
  
      NSDate *other_date;
      other_date = [NSDate dateWithTimeIntervalSinceNow:interval];
  
      NSString *d1, *d2;
      d1 = [df stringFromDate:date];
      d2 = [df stringFromDate:other_date];
      return [d1 isEqualToString:d2];    
  }
  
  - (BOOL)dateIsToday:(NSDate *)date {
      return [self date:date isDayWithTimeIntervalSinceNow:0];
  }
  
  - (BOOL)dateIsYesterday:(NSDate *)date {
      return [self date:date isDayWithTimeIntervalSinceNow:-86400];
  }
  
  - (BOOL)dateIsTwoToSixDaysAgo:(NSDate *)date {
      for (int i = 2; i <= 6; i += 1)
          if ([self date:date isDayWithTimeIntervalSinceNow:i*-86400])
              return YES;
      return NO;    
  }
  
  - (NSString *)dateAsStringDate:(NSDate *)date {
      NSDateFormatter *df = [[NSDateFormatter alloc] init];
      [df setDateStyle:NSDateFormatterShortStyle];
      [df setDoesRelativeDateFormatting:YES];
      NSString *str = [df stringFromDate:date];
      return str;
  }
  
  - (NSString *)dateAsStringTime:(NSDate *)date {
      NSDateFormatter *df = [[NSDateFormatter alloc] init];
      [df setTimeStyle:NSDateFormatterShortStyle];
      NSString *str = [df stringFromDate:date];
      return str;
  }
  
  - (NSString *)dateAsStringDay:(NSDate *)date {
      NSDateFormatter *df = [[NSDateFormatter alloc] init];
      [df setDateFormat:@"EEEE"];
      NSString *str_day = [df stringFromDate:date];
      return str_day;
  }
  

As mentioned in yours and Brad's answers, you can obtain an NSDate from a timestamp using NSDate's dateWithTimeIntervalSince1970.

Answer 2

I made this method to change the unix time stamp into a nice readable, relative string. Probably doesn't work properly in the first few days of a new year, but hopefully you should be too hungover to notice.

-(NSString *)relativeTime:(int)datetimestamp
{
    NSDate *aDate = [NSDate dateWithTimeIntervalSince1970:datetimestamp];
    NSCalendar *calendar = [NSCalendar currentCalendar];
    unsigned int unitFlags =  NSYearCalendarUnit|NSMonthCalendarUnit|NSWeekCalendarUnit|NSWeekdayOrdinalCalendarUnit|NSWeekdayCalendarUnit|NSDayCalendarUnit|NSHourCalendarUnit|NSMinuteCalendarUnit;
    NSDateComponents *messageDateComponents = [calendar components:unitFlags fromDate:aDate];
    NSDateComponents *todayDateComponents = [calendar components:unitFlags fromDate:[NSDate date]];

    NSUInteger dayOfYearForMessage = [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSYearCalendarUnit forDate:aDate];
    NSUInteger dayOfYearForToday = [calendar ordinalityOfUnit:NSDayCalendarUnit inUnit:NSYearCalendarUnit forDate:[NSDate date]];


    NSString *dateString;

    if ([messageDateComponents year] == [todayDateComponents year] && 
        [messageDateComponents month] == [todayDateComponents month] &&
        [messageDateComponents day] == [todayDateComponents day]) 
    {
        dateString = [NSString stringWithFormat:@"%02d:%02d", [messageDateComponents hour], [messageDateComponents minute]];
    } else if ([messageDateComponents year] == [todayDateComponents year] && 
               dayOfYearForMessage == (dayOfYearForToday-1))
    {
        dateString = @"Yesterday";
    } else if ([messageDateComponents year] == [todayDateComponents year] &&
               dayOfYearForMessage > (dayOfYearForToday-6))
    {

        NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
        [dateFormatter setDateFormat:@"EEEE"];
        dateString = [dateFormatter stringFromDate:aDate];
        [dateFormatter release];

    } else {

        NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
        [dateFormatter setDateFormat:@"yy"];
        dateString = [NSString stringWithFormat:@"%02d/%02d/%@", [messageDateComponents day], [messageDateComponents month], [dateFormatter stringFromDate:aDate]];
        [dateFormatter release];
    }

    return dateString;
}