A PHP class to turn a timestamp into more user-friendly relative date.

php-relative-date-class.php

/**
 * A class for turning timestamps into more user-friendly relative dates.
 *
$date = new Relative_Date();

echo $date->relative_formatted_date; //"Today"
 */
class Relative_Date {
	
	const DAY = 86400;
	public $timestamp; //keep timestamp used to instantiate object
	public $daystamp; //timestamp for that day, 12:00:00
	public $info; //getdate() info (Array)
	public $day_of_week; //string day of week, ex. "Monday" 
	public $relative_formatted_date; //string of date compared to today - "Today", "Yesterday", "x days ago", etc.
	public $formatted_date; //string of date compared to today - "Today", "Yesterday", "Wednesday", "Tuesday", etc.
	
	
	public function __construct($timestamp = null){
		if(empty($timestamp)){
			$timestamp = time();
		}
		if(is_string($timestamp)){
			$timestamp = strtotime($timestamp);
		}
				
		$this->timestamp = $timestamp;
		
		$this->info = getdate($timestamp);
		
		$this->daystamp = mktime(0, 0, 0, $this->info['mon'], $this->info['mday'], $this->info['year']);
		
		$this->day_of_week = $this->info['weekday']; //"Friday"
		
		$this->relative_formatted_date = $this->get_formatted_date(true); //"Today"|"Yesterday"|"x days ago" 
		
		$this->formatted_date = $this->get_formatted_date(); //"Today"|"Yesterday"|"Wednesday"
	}	
		
	/**
	 * 
	 * @param int $timestamp [optional]
	 * @return the number of days between this App_Date object and a given timestamp (0: today, 1+: future, -1: past)
	 */
	public function get_day_difference($timestamp = null){
		if(empty($timestamp)){
			$timestamp = time();
		}
		//get # of days in first timestamp
		$first = $this->timestamp/self::DAY;
		
		//get # of days in second timestamp
		$second = $timestamp/self::DAY;
		
		//get difference in days
		$difference = floor($second) - floor($first);
		
		return $difference;
	}
	
	/**
	 * gets the previous working day (Friday before a Monday, or M-Th otherwise)
	 * @return previous working day as an instance of App_Date 
	 */
	public function get_previous_working_day(){
		$date = $this->info;
		$day_of_month = $date['mday'];
		$day_of_week = $date['wday'];

		if($day_of_week == 0){
			//is Sunday, get Friday
			$previous_work_day = $day_of_month - 2;
		}
		elseif($day_of_week == 1){
			//is Monday, get Friday
			$previous_work_day = $day_of_month - 3;
		} else {
			//is any other day of the week, get previous
			$previous_work_day = $day_of_month - 1;
		}
		
		$timestamp = mktime($date['hours'], $date['minutes'], $date['seconds'], $date['mon'], $previous_work_day, $date['year']);
		
		$new_date = new App_Date($timestamp);
		return $new_date;
	}
	
	/**
	 * gets the next working day (Monday after a Friday, or other Tues-F otherwise)
	 * @return next working day as an instance of App_Date 
	 */
	public function get_next_working_day(){
		$date = $this->info;
		$day_of_month = $date['mday'];
		$day_of_week = $date['wday'];

		if($day_of_week == 5){
			//is Friday, get Monday
			$next_work_day = $day_of_month + 3;
		}
		elseif($day_of_week == 6){
			//is Saturday, get Monday
			$next_work_day = $day_of_month + 2;
		} else {
			//is any other day of the week, get previous
			$next_work_day = $day_of_month + 1;
		}
		
		$timestamp = mktime($date['hours'], $date['minutes'], $date['seconds'], $date['mon'], $next_work_day, $date['year']);
		
		$new_date = new App_Date($timestamp);
		return $new_date;
	}
	
	/**
	 * A helper function for getting many previous work days (including current day) - NOTE that this returns an array of App_Date objects
	 * @param object $number_of_days [optional]
	 * @return Array of App_Date instances
	 */
	public function get_previous_working_days($number_of_days = 1){
		$working_days = array();
		//beginning date is this
		$current_date = $this;	
		 
		for($i = 0; $i < $number_of_days; $i++){			
			$working_days[] = $current_date;
			
			$new_date = new App_Date($current_date->timestamp);
			
			$current_date = $new_date->get_previous_working_day();
			
		}
		return $working_days;				
	}
	
	/**
	 * Get the formatted string based on relationship of current object's week to the current (actual) week
	 * @return formatted string  
	 */
	public function get_formatted_week(){
		$difference = $this->get_week_difference();
		
		if($difference == 0){
			return "This Week";
		}
		elseif($difference == -1){
			return "Last Week";
		} 
		elseif($difference == 1){
			return "Next Week"; 
		}
		else {
			$date = $this->info;
			//get day of month
			$mday = $date['mday']; 
			//get day of week
			$wday = $date['wday']; 
			//get the day of the month that is the Sunday of the current week
			$sunday = $mday - $wday; 
			$timestamp = mktime($date['hours'], $date['minutes'], $date['seconds'], $date['mon'], $sunday, $date['year']);
			return 'Week of ' . date('F j, Y', $timestamp);
		}		
	}
	
	/**
	 * get the difference in weeks between two timestamps, within the context of a business week
	 * e.g. A Monday of the current week is in a different week than the previous Friday, despite the difference being < 7 days
	 * @param object $timestamp [optional]
	 * @return 
	 */
	public function get_week_difference($timestamp = null){
		if(empty($timestamp)){
			$timestamp = time();
		}

		//date('W') assumes week starts on Monday
		$week_of_year = date('W', $this->timestamp);
		$other_week_of_year = date('W', $timestamp);
		
		$difference = $week_of_year - $other_week_of_year;
		
		return $difference;
	}
	
	/**
	 * Return formatted string determining if $this date is "Tomorrow", "Today", "Yesterday" or "X days ago"
	 * @return a string representing how "now" compares to calling object 
	 */
	public function get_formatted_date($relative = false, $unix_date = null){
		if(empty($unix_date)){
			$unix_date = $this->timestamp;
		} 			
		
		$periods         = array("second", "minute", "hour", "day", "week", "month", "year", "decade");
		$lengths         = array("60","60","24","7","4.35","12","10");
		
		$now = time();
		
		// is it future date or past date
		if($now > $unix_date) {
			//past date   
		    $difference     = $now - $unix_date;
		    $tense         = "ago";
		   
		} else {
			//future date
		    $difference     = $unix_date - $now;
		    $tense         = "from now";
		}
		
		$formatted_date = "Incorrect format.";
		
		$day_difference = $this->get_day_difference();
		
		//if difference is less than a day, check for yesterday, tomorrow, or today; 
		if($day_difference <= 1 && $day_difference >= -1){
			if($day_difference == 1){
				$formatted_date = "Yesterday";
			}
			elseif($day_difference == 0){
				$formatted_date = "Today";
			}
			else {
				$formatted_date = "Tomorrow";
			}
		} 
		elseif($relative) {
			//difference is more than a day and the format should be "relative"
			for($j = 0; $difference >= $lengths[$j] && $j < count($lengths)-1; $j++) {
			    $difference /= $lengths[$j];
			}
			
			$difference = round($difference);
			
			if($difference != 1) {
			    $periods[$j].= "s";
			}
			$formatted_date = "$difference $periods[$j] {$tense}";
		}
		else {
			//difference is more than a day and the format should NOT be "relative"
			$formatted_date = $this->day_of_week;
		}
				
		return $formatted_date;
	}	
}