class-expressivedate.php

<?php

/**
 *  @method int getDay() Get day of month.
 *  @method int getMonth() Get the month.
 *  @method int getYear() Get the year.
 *  @method int getHour() Get the hour.
 *  @method int getMinute() Get the minutes.
 *  @method int getSecond() Get the seconds.
 *  @method string getDayOfWeek() Get the day of the week, e.g., Monday.
 *  @method int getDayOfWeekAsNumeric() Get the numeric day of week.
 *  @method int getDaysInMonth() Get the number of days in the month.
 *  @method int getDayOfYear() Get the day of the year.
 *  @method string getDaySuffix() Get the suffix of the day, e.g., st.
 *  @method bool isLeapYear() Determines if is leap year.
 *  @method string isAmOrPm() Determines if time is AM or PM.
 *  @method bool isDaylightSavings() Determines if observing daylight savings.
 *  @method int getGmtDifference() Get difference in GMT.
 *  @method int getGmtDifferenceColon() Get difference in GMT with Colon between hours and minutes.
 *  @method int getSecondsSinceEpoch() Get the number of seconds since epoch.
 *  @method string getTimezoneName() Get the timezone name.
 *  @method setDay(int $day) Set the day of month.
 *  @method setMonth(int $month) Set the month.
 *  @method setYear(int $year) Set the year.
 *  @method setHour(int $hour) Set the hour.
 *  @method setMinute(int $minute) Set the minutes.
 *  @method setSecond(int $second) Set the seconds.
 */

class ExpressiveDate extends DateTime {

	/**
	 * Default date format used when casting object to string.
	 *
	 * @var string
	 */
	protected $defaultDateFormat = 'jS F, Y \a\\t g:ia';

	/**
	 * Starting day of the week, where 0 is Sunday and 1 is Monday.
	 *
	 * @var int
	 */
	protected $weekStartDay = 0;

	/**
	 * Create a new ExpressiveDate instance.
	 *
	 * @param  string  $time
	 * @param  string|DateTimeZone  $timezone
	 * @return void
	 */
	public function __construct( $time = 'now', $timezone = null ) {
		if ( ! empty( $timezone ) ) {
			$timezone = $this->parseSuppliedTimezone( $timezone );
		}

		parent::__construct( $time, $timezone );
	}

	/**
	 * Make and return new ExpressiveDate instance.
	 *
	 * @param  string  $time
	 * @param  string|DateTimeZone  $timezone
	 * @return ExpressiveDate
	 */
	public static function make( $time = 'now', $timezone = null ): ExpressiveDate {
		return new static( $time, $timezone );
	}

	/**
	 * Make and return a new ExpressiveDate instance with defined year, month, and day.
	 *
	 * @param  int  $year
	 * @param  int  $month
	 * @param  int  $day
	 * @param  string|DateTimeZone  $timezone
	 * @return ExpressiveDate
	 */
	public static function makeFromDate( $year = null, $month = null, $day = null, $timezone = null ): ExpressiveDate {
		return static::makeFromDateTime( $year, $month, $day, null, null, null, $timezone );
	}

	/**
	 * Make and return a new ExpressiveDate instance with defined hour, minute, and second.
	 *
	 * @param  int  $hour
	 * @param  int  $minute
	 * @param  int  $second
	 * @param  string|DateTimeZone  $timezone
	 * @return ExpressiveDate
	 */
	public static function makeFromTime( $hour = null, $minute = null, $second = null, $timezone = null ): ExpressiveDate {
		return static::makeFromDateTime( null, null, null, $hour, $minute, $second, $timezone );
	}

	/**
	 * Make and return a new ExpressiveDate instance with defined year, month, day, hour, minute, and second.
	 *
	 * @param  int  $year
	 * @param  int  $month
	 * @param  int  $day
	 * @param  int  $hour
	 * @param  int  $minute
	 * @param  int  $second
	 * @param  string|DateTimeZone  $timezone
	 * @return ExpressiveDate
	 */
	public static function makeFromDateTime( $year = null, $month = null, $day = null, $hour = null, $minute = null, $second = null, $timezone = null ): ExpressiveDate {
		$date = new static( 'now', $timezone );

		$date->setDate( ! empty( $year ) ? $year : $date->getYear(), ! empty( $month ) ? $month : $date->getMonth(), ! empty( $day ) ? $day : $date->getDay() );

		if ( is_null( $hour ) ) {
			$hour = $date->getHour();
		}
		if ( is_null( $minute ) ) {
			$minute = $date->getMinute();
		}
		if ( is_null( $second ) ) {
			$second = 0;
		}
		$date->setTime( $hour, $minute, $second );

		return $date;
	}

	public static function createFromFormat( $format, $datestring, $timezone = null ): ExpressiveDate {
		$parent_date = parent::createFromFormat( $format, $datestring );
		if ( $parent_date !== false ) {
			$year  = $parent_date->format( 'Y' );
			$month = $parent_date->format( 'n' );
			$day   = $parent_date->format( 'j' );
			$hour  = $parent_date->format( 'G' );
			$min   = $parent_date->format( 'i' );
			$sec   = $parent_date->format( 's' );
			return static::makeFromDateTime( $year, $month, $day, $hour, $min, $sec, $timezone );
		} else {
			return false;
		}
	}

	/**
	 * Parse a supplied timezone.
	 *
	 * @param  string|DateTimeZone  $timezone
	 * @return DateTimeZone
	 */
	public static function parseSuppliedTimezone( $timezone ): DateTimeZone {
		if ( $timezone instanceof DateTimeZone or is_null( $timezone ) ) {
			return $timezone;
		}

		try {
			$timezone = new DateTimeZone( $timezone );
		} catch ( Exception $error ) {
			throw new InvalidArgumentException( 'The supplied timezone [' . $timezone . '] is not supported.' );
		}

		return $timezone;
	}

	/**
	 * Use the current date and time.
	 *
	 * @return ExpressiveDate
	 */
	public function now(): ExpressiveDate {
		$this->setTimestamp( time() );

		return $this;
	}

	/**
	 * Use today's date and time at midnight.
	 *
	 * @return ExpressiveDate
	 */
	public function today(): ExpressiveDate {
		$this->now()->setHour( 0 )->setMinute( 0 )->setSecond( 0 );

		return $this;
	}

	/**
	 * Use tomorrow's date and time at midnight.
	 *
	 * @return ExpressiveDate
	 */
	public function tomorrow(): ExpressiveDate {
		$this->now()->addOneDay()->startOfDay();

		return $this;
	}

	/**
	 * Use yesterday's date and time at midnight.
	 *
	 * @return ExpressiveDate
	 */
	public function yesterday(): ExpressiveDate {
		$this->now()->minusOneDay()->startOfDay();

		return $this;
	}

	/**
	 * Use the start of the day.
	 *
	 * @return ExpressiveDate
	 */
	public function startOfDay(): ExpressiveDate {
		$this->setHour( 0 )->setMinute( 0 )->setSecond( 0 );

		return $this;
	}

	/**
	 * Use the end of the day.
	 *
	 * @return ExpressiveDate
	 */
	public function endOfDay(): ExpressiveDate {
		$this->setHour( 23 )->setMinute( 59 )->setSecond( 59 );

		return $this;
	}

	/**
	 * Use the start of the week.
	 *
	 * @return ExpressiveDate
	 */
	public function startOfWeek(): ExpressiveDate {
		$this->minusDays( $this->getDayOfWeekAsNumeric() )->startOfDay();

		return $this;
	}

	/**
	 * Use the end of the week.
	 *
	 * @return ExpressiveDate
	 */
	public function endOfWeek(): ExpressiveDate {
		$this->addDays( 6 - $this->getDayOfWeekAsNumeric() )->endOfDay();

		return $this;
	}

	/**
	 * Use the start of the month.
	 *
	 * @return ExpressiveDate
	 */
	public function startOfMonth(): ExpressiveDate {
		$this->setDay( 1 )->startOfDay();

		return $this;
	}

	/**
	 * Use the end of the month.
	 *
	 * @return ExpressiveDate
	 */
	public function endOfMonth(): ExpressiveDate {
		$this->setDay( $this->getDaysInMonth() )->endOfDay();

		return $this;
	}

	/**
	 * Add one day.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addOneDay(): ExpressiveDate {
		return $this->modifyDays( 1 );
	}

	/**
	 * Add a given amount of days.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addDays( $amount ): ExpressiveDate {
		return $this->modifyDays( $amount );
	}

	/**
	 * Minus one day.
	 *
	 * @return ExpressiveDate
	 */
	public function minusOneDay(): ExpressiveDate {
		return $this->modifyDays( 1, true );
	}

	/**
	 * Minus a given amount of days.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function minusDays( $amount ): ExpressiveDate {
		$amount = floatval($amount);
		// minusDays and a negative amount is in fact addDays
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			return $this->modifyDays( $amount );
		} else {
			return $this->modifyDays( $amount, true );
		}
	}

	/**
	 * Modify by an amount of days.
	 *
	 * @param  int  $amount
	 * @param  bool  $invert
	 * @return ExpressiveDate
	 */
	public function modifyDays( $amount, $invert = false ) {
		$amount = floatval($amount);
		if (empty($amount)) {
			return $this;
		}
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			$invert = true;
		}
		if ( $this->isFloat( $amount ) ) {
			return $this->modifyHours( $amount * 24, $invert );
		}

		$interval = new DateInterval( "P{$amount}D" );

		$this->modifyFromInterval( $interval, $invert );

		return $this;
	}

	/**
	 * Add one month.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addOneMonth() {
		return $this->modifyMonths( 1 );
	}

	/**
	 * Add a given amount of months.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addMonths( $amount ) {
		return $this->modifyMonths( $amount );
	}

	/**
	 * Minus one month.
	 *
	 * @return ExpressiveDate
	 */
	public function minusOneMonth() {
		return $this->modifyMonths( 1, true );
	}

	/**
	 * Minus a given amount of months.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function minusMonths( $amount ) {
		$amount = floatval($amount);
		// minusMonths and a negative amount is in fact addMonths
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			return $this->modifyMonths( $amount );
		} else {
			return $this->modifyMonths( $amount, true );
		}
	}

	/**
	 * Modify by an amount of months.
	 *
	 * @param  int  $amount
	 * @param  bool  $invert
	 * @return ExpressiveDate
	 */
	public function modifyMonths( $amount, $invert = false ) {
		$amount = floatval($amount);
		if (empty($amount)) {
			return $this;
		}
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			$invert = true;
		}
		if ( $this->isFloat( $amount ) ) {
			return $this->modifyWeeks( $amount * 4, $invert );
		}

		$interval = new DateInterval( "P{$amount}M" );

		$this->modifyFromInterval( $interval, $invert );

		return $this;
	}

	/**
	 * Add one year.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addOneYear() {
		return $this->modifyYears( 1 );
	}

	/**
	 * Add a given amount of years.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addYears( $amount ) {
		return $this->modifyYears( $amount );
	}

	/**
	 * Minus one year.
	 *
	 * @return ExpressiveDate
	 */
	public function minusOneYear() {
		return $this->modifyYears( 1, true );
	}

	/**
	 * Minus a given amount of years.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function minusYears( $amount ) {
		$amount = floatval($amount);
		// minusYears and a negative amount is in fact addYears
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			return $this->modifyYears( $amount );
		} else {
			return $this->modifyYears( $amount, true );
		}
	}

	/**
	 * Modify by an amount of Years.
	 *
	 * @param  int  $amount
	 * @param  bool  $invert
	 * @return ExpressiveDate
	 */
	public function modifyYears( $amount, $invert = false ) {
		$amount = floatval($amount);
		if (empty($amount)) {
			return $this;
		}
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			$invert = true;
		}
		if ( $this->isFloat( $amount ) ) {
			return $this->modifyMonths( $amount * 12, $invert );
		}

		$interval = new DateInterval( "P{$amount}Y" );

		$this->modifyFromInterval( $interval, $invert );

		return $this;
	}

	/**
	 * Add one hour.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addOneHour() {
		return $this->modifyHours( 1 );
	}

	/**
	 * Add a given amount of hours.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addHours( $amount ) {
		return $this->modifyHours( $amount );
	}

	/**
	 * Minus one hour.
	 *
	 * @return ExpressiveDate
	 */
	public function minusOneHour() {
		return $this->modifyHours( 1, true );
	}

	/**
	 * Minus a given amount of hours.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function minusHours( $amount ) {
		$amount = floatval($amount);
		// minusHours and a negative amount is in fact addHours
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			return $this->modifyHours( $amount );
		} else {
			return $this->modifyHours( $amount, true );
		}
	}

	/**
	 * Modify by an amount of hours.
	 *
	 * @param  int  $amount
	 * @param  bool  $invert
	 * @return ExpressiveDate
	 */
	public function modifyHours( $amount, $invert = false ) {
		$amount = floatval($amount);
		if (empty($amount)) {
			return $this;
		}
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			$invert = true;
		}
		if ( $this->isFloat( $amount ) ) {
			return $this->modifyMinutes( $amount * 60, $invert );
		}

		$interval = new DateInterval( "PT{$amount}H" );

		$this->modifyFromInterval( $interval, $invert );

		return $this;
	}

	/**
	 * Add one minute.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addOneMinute() {
		return $this->modifyMinutes( 1 );
	}

	/**
	 * Add a given amount of minutes.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addMinutes( $amount ) {
		return $this->modifyMinutes( $amount );
	}

	/**
	 * Minus one minute.
	 *
	 * @return ExpressiveDate
	 */
	public function minusOneMinute() {
		return $this->modifyMinutes( 1, true );
	}

	/**
	 * Minus a given amount of minutes.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function minusMinutes( $amount ) {
		$amount = floatval($amount);
		// minusMinutes and a negative amount is in fact addMinutes
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			return $this->modifyMinutes( $amount );
		} else {
			return $this->modifyMinutes( $amount, true );
		}
	}

	/**
	 * Modify by an amount of minutes.
	 *
	 * @param  int  $amount
	 * @param  bool  $invert
	 * @return ExpressiveDate
	 */
	public function modifyMinutes( $amount, $invert = false ) {
		$amount = floatval($amount);
		if (empty($amount)) {
			return $this;
		}
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			$invert = true;
		}
		if ( $this->isFloat( $amount ) ) {
			return $this->modifySeconds( $amount * 60, $invert );
		}

		$interval = new DateInterval( "PT{$amount}M" );

		$this->modifyFromInterval( $interval, $invert );

		return $this;
	}

	/**
	 * Add one second.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addOneSecond() {
		return $this->modifySeconds( 1 );
	}

	/**
	 * Add a given amount of seconds.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addSeconds( $amount ) {
		return $this->modifySeconds( $amount );
	}

	/**
	 * Minus one second.
	 *
	 * @return ExpressiveDate
	 */
	public function minusOneSecond() {
		return $this->modifySeconds( 1, true );
	}

	/**
	 * Minus a given amount of seconds.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function minusSeconds( $amount ) {
		$amount = floatval($amount);
		// minusSeconds and a negative amount is in fact addSeconds
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			return $this->modifySeconds( $amount );
		} else {
			return $this->modifySeconds( $amount, true );
		}
	}

	/**
	 * Modify by an amount of seconds.
	 *
	 * @param  int  $amount
	 * @param  bool  $invert
	 * @return ExpressiveDate
	 */
	public function modifySeconds( $amount, $invert = false ) {
		// seconds are the smallest unit here and need to be an integer, otherwise DateInterval will complain
		$amount = intval($amount);
		if (empty($amount)) {
			return $this;
		}
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			$invert = true;
		}
		$interval = new DateInterval( "PT{$amount}S" );

		$this->modifyFromInterval( $interval, $invert );

		return $this;
	}

	/**
	 * Add one week.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addOneWeek() {
		return $this->modifyWeeks( 1 );
	}

	/**
	 * Add a given amount of weeks.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function addWeeks( $amount ) {
		return $this->modifyWeeks( $amount );
	}

	/**
	 * Minus one week.
	 *
	 * @return ExpressiveDate
	 */
	public function minusOneWeek() {
		return $this->modifyWeeks( 1, true );
	}

	/**
	 * Minus a given amount of weeks.
	 *
	 * @param  int  $amount
	 * @return ExpressiveDate
	 */
	public function minusWeeks( $amount ) {
		// minusWeeks and a negative amount is in fact addWeeks
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			return $this->modifyWeeks( $amount );
		} else {
			return $this->modifyWeeks( $amount, true );
		}
	}

	/**
	 * Modify by an amount of weeks.
	 *
	 * @param  int  $amount
	 * @param  bool  $invert
	 * @return ExpressiveDate
	 */
	public function modifyWeeks( $amount, $invert = false ) {
		$amount = floatval($amount);
		if (empty($amount)) {
			return $this;
		}
		if ( $amount < 0 ) {
			$amount = abs( $amount );
			$invert = true;
		}
		if ( $this->isFloat( $amount ) ) {
			return $this->modifyDays( $amount * 7, $invert );
		}

		$interval = new DateInterval( "P{$amount}W" );

		$this->modifyFromInterval( $interval, $invert );

		return $this;
	}

	/**
	 * Modify from a DateInterval object.
	 *
	 * @param  DateInterval  $interval
	 * @param  bool  $invert
	 * @return ExpressiveDate
	 */
	public function modifyFromInterval( $interval, $invert = false ): ExpressiveDate {
		if ( $invert ) {
			$this->sub( $interval );
		} else {
			$this->add( $interval );
		}

		return $this;
	}

	/**
	 * Set the timezone.
	 *
	 * @param  string|DateTimeZone  $timezone
	 * @return ExpressiveDate
	 */
	public function setTimezone( $timezone ): ExpressiveDate {
		if ( ! empty( $timezone ) ) {
			$timezone = $this->parseSuppliedTimezone( $timezone );
		}

		if ( $timezone instanceof DateTimeZone ) {
			parent::setTimezone( $timezone );
		}

		return $this;
	}

	/**
	 * Sets the timestamp from a human readable string.
	 *
	 * @param  string  $string
	 * @return ExpressiveDate
	 */
	public function setTimestampFromString( $string ): ExpressiveDate {
		$this->setTimestamp( strtotime( $string ) );

		return $this;
	}

	/**
	 * Determine if day is a weekday.
	 *
	 * @return bool
	 */
	public function isWeekday(): bool {
		$day = $this->getDayOfWeek();

		return ! in_array( $day, [ 'Saturday', 'Sunday' ] );
	}

	/**
	 * Determine if day is a weekend.
	 *
	 * @return bool
	 */
	public function isWeekend(): bool {
		return ! $this->isWeekday();
	}

	/**
	 * Get the difference in years.
	 *
	 * @param  ExpressiveDate  $compare
	 * @return string
	 */
	public function getDifferenceInYears( $compare = null ): string {
		if ( ! $compare ) {
			$compare = new ExpressiveDate( 'now', $this->getTimezone() );
		}

		return $this->diff( $compare )->format( '%r%y' );
	}

	/**
	 * Get the difference in months.
	 *
	 * @param  ExpressiveDate  $compare
	 * @return string
	 */
	public function getDifferenceInMonths( $compare = null ): string {
		if ( ! $compare ) {
			$compare = new ExpressiveDate( 'now', $this->getTimezone() );
		}

		$difference = $this->diff( $compare );

		[$years, $months] = explode( ':', $difference->format( '%y:%m' ) );

		return ( ( $years * 12 ) + $months ) * $difference->format( '%r1' );
	}

	/**
	 * Get the difference in days.
	 *
	 * @param  ExpressiveDate  $compare
	 * @return string
	 */
	public function getDifferenceInDays( $compare = null ): string {
		if ( ! $compare ) {
			$compare = new ExpressiveDate( 'now', $this->getTimezone() );
		}

		$res = $this->diff( $compare )->format( '%r%a' );
		// we don't want to return "-0" ...
		if ( abs( $res ) == 0 ) {
			return 0;
		} else {
			return $res;
		}
	}

	/**
	 * Get the difference in hours.
	 *
	 * @param  ExpressiveDate  $compare
	 * @return string
	 */
	public function getDifferenceInHours( $compare = null ) {
		return $this->getDifferenceInMinutes( $compare ) / 60;
	}

	/**
	 * Get the difference in minutes.
	 *
	 * @param  ExpressiveDate  $compare
	 * @return string
	 */
	public function getDifferenceInMinutes( $compare = null ) {
		return $this->getDifferenceInSeconds( $compare ) / 60;
	}

	/**
	 * Get the difference in seconds.
	 *
	 * @param  ExpressiveDate  $compare
	 * @return string
	 */
	public function getDifferenceInSeconds( $compare = null ) {
		if ( ! $compare ) {
			$compare = new ExpressiveDate( 'now', $this->getTimezone() );
		}

		$difference = $this->diff( $compare );

		[$days, $hours, $minutes, $seconds] = explode( ':', $difference->format( '%a:%h:%i:%s' ) );

		// Add the total amount of seconds in all the days.
		$seconds += ( $days * 24 * 60 * 60 );

		// Add the total amount of seconds in all the hours.
		$seconds += ( $hours * 60 * 60 );

		// Add the total amount of seconds in all the minutes.
		$seconds += ( $minutes * 60 );

		return $seconds * $difference->format( '%r1' );
	}

	/**
	 * Get a relative date string, e.g., 3 days ago.
	 *
	 * @param  ExpressiveDate  $compare
	 * @return string
	 */
	public function getRelativeDate( $compare = null ) {
		if ( ! $compare ) {
			$compare = new ExpressiveDate( 'now', $this->getTimezone() );
		}

		$units  = [ 'second', 'minute', 'hour', 'day', 'week', 'month', 'year' ];
		$values = [ 60, 60, 24, 7, 4.35, 12 ];

		// Get the difference between the two timestamps. We'll use this to cacluate the
		// actual time remaining.
		$difference = abs( $compare->getTimestamp() - $this->getTimestamp() );

		for ( $i = 0; $i < count( $values ) and $difference >= $values[ $i ]; $i++ ) {
			$difference = $difference / $values[ $i ];
		}

		// Round the difference to the nearest whole number.
		$difference = round( $difference );

		if ( $compare->getTimestamp() < $this->getTimestamp() ) {
			$suffix = 'from now';
		} else {
			$suffix = 'ago';
		}

		// Get the unit of time we are measuring. We'll then check the difference, if it is not equal
		// to exactly 1 then it's a multiple of the given unit so we'll append an 's'.
		$unit = $units[ $i ];

		if ( $difference != 1 ) {
			$unit .= 's';
		}

		return $difference . ' ' . $unit . ' ' . $suffix;
	}

	/**
	 * Get a date string in the format of 2012-12-04.
	 *
	 * @return string
	 */
	public function getDate() {
		return $this->format( 'Y-m-d' );
	}

	/**
	 * Get a date and time string in the format of 2012-12-04 23:43:27.
	 *
	 * @return string
	 */
	public function getDateTime() {
		return $this->format( 'Y-m-d H:i:s' );
	}

	/**
	 * Get a date string in the format of Jan 31, 1991.
	 *
	 * @return string
	 */
	public function getShortDate() {
		return $this->format( 'M j, Y' );
	}

	/**
	 * Get a date string in the format of January 31st, 1991 at 7:45am.
	 *
	 * @return string
	 */
	public function getLongDate() {
		return $this->format( 'F jS, Y \a\\t g:ia' );
	}

	/**
	 * Get a date string in the format of 07:42:32.
	 *
	 * @return string
	 */
	public function getTime() {
		return $this->format( 'H:i:s' );
	}

	/**
	 * Get a date string in the default format.
	 *
	 * @return string
	 */
	public function getDefaultDate() {
		return $this->format( $this->defaultDateFormat );
	}

	/**
	 * Set the default date format.
	 *
	 * @param  string  $format
	 * @return ExpressiveDate
	 */
	public function setDefaultDateFormat( $format ): ExpressiveDate {
		$this->defaultDateFormat = $format;

		return $this;
	}

	/**
	 * Set the starting day of the week, where 0 is Sunday and 1 is Monday.
	 *
	 * @param int|string $weekStartDay
	 * @return void
	 */
	public function setWeekStartDay( $weekStartDay ) {
		if ( is_numeric( $weekStartDay ) ) {
			$this->weekStartDay = $weekStartDay;
		} else {
			$this->weekStartDay = array_search( strtolower( $weekStartDay ), [ 'sunday', 'monday' ] );
		}

		return $this;
	}

	/**
	 * Get the starting day of the week, where 0 is Sunday and 1 is Monday
	 *
	 * @return int
	 */
	public function getWeekStartDay(): int {
		return $this->weekStartDay;
	}

	/**
	 * Get a date attribute.
	 *
	 * @param  string  $attribute
	 * @return mixed
	 */
	protected function getDateAttribute( $attribute ) {
		switch ( $attribute ) {
			case 'Day':
				return $this->format( 'd' );
				break;
			case 'Month':
				return $this->format( 'm' );
				break;
			case 'Year':
				return $this->format( 'Y' );
				break;
			case 'Hour':
				return $this->format( 'G' );
				break;
			case 'Minute':
				return $this->format( 'i' );
				break;
			case 'Second':
				return $this->format( 's' );
				break;
			case 'DayOfWeek':
				return $this->format( 'l' );
				break;
			case 'DayOfWeekAsNumeric':
				return ( 7 + $this->format( 'w' ) - $this->getWeekStartDay() ) % 7;
				break;
			case 'DaysInMonth':
				return $this->format( 't' );
				break;
			case 'DayOfYear':
				return $this->format( 'z' );
				break;
			case 'DaySuffix':
				return $this->format( 'S' );
				break;
			case 'GmtDifference':
				return $this->format( 'O' );
				break;
			case 'GmtDifferenceColon':
				return $this->format( 'P' );
				break;
			case 'SecondsSinceEpoch':
				return $this->format( 'U' );
				break;
			case 'TimezoneName':
				return $this->getTimezone()->getName();
				break;
		}

		throw new InvalidArgumentException( 'The date attribute [' . $attribute . '] could not be found.' );
	}

	/**
	 * Syntactical sugar for determining if date object "is" a condition.
	 *
	 * @param  string  $attribute
	 * @return bool
	 */
	protected function isDateAttribute( $attribute ): bool {
		switch ( $attribute ) {
			case 'LeapYear':
				return (bool) $this->format( 'L' );
				break;
			case 'AmOrPm':
				return $this->format( 'A' );
				break;
			case 'DaylightSavings':
				return (bool) $this->format( 'I' );
				break;
		}

		throw new InvalidArgumentException( 'The date attribute [' . $attribute . '] could not be found.' );
	}

	/**
	 * Set a date attribute.
	 *
	 * @param  string  $attribute
	 * @return ExpressiveDate
	 */
	protected function setDateAttribute( $attribute, $value ): ExpressiveDate {
		switch ( $attribute ) {
			case 'Day':
				return $this->setDate( $this->getYear(), $this->getMonth(), $value );
				break;
			case 'Month':
				return $this->setDate( $this->getYear(), $value, $this->getDay() );
				break;
			case 'Year':
				return $this->setDate( $value, $this->getMonth(), $this->getDay() );
				break;
			case 'Hour':
				return $this->setTime( $value, $this->getMinute(), $this->getSecond() );
				break;
			case 'Minute':
				return $this->setTime( $this->getHour(), $value, $this->getSecond() );
				break;
			case 'Second':
				return $this->setTime( $this->getHour(), $this->getMinute(), $value );
				break;
		}

		throw new InvalidArgumentException( 'The date attribute [' . $attribute . '] could not be set.' );
	}

	/**
	 * Alias for ExpressiveDate::equalTo()
	 *
	 * @param  ExpressiveDate  $date
	 * @return bool
	 */
	public function sameAs( ExpressiveDate $date ): bool {
		return $this->equalTo( $date );
	}

	/**
	 * Determine if date is equal to another Expressive Date instance.
	 *
	 * @param  ExpressiveDate  $date
	 * @return bool
	 */
	public function equalTo( ExpressiveDate $date ): bool {
		return $this == $date;
	}

	/**
	 * Determine if date is not equal to another Expressive Date instance.
	 *
	 * @param  ExpressiveDate  $date
	 * @return bool
	 */
	public function notEqualTo( ExpressiveDate $date ): bool {
		return ! $this->equalTo( $date );
	}

	/**
	 * Determine if date is greater than another Expressive Date instance.
	 *
	 * @param  ExpressiveDate  $date
	 * @return bool
	 */
	public function greaterThan( ExpressiveDate $date ): bool {
		return $this > $date;
	}

	/**
	 * Determine if date is less than another Expressive Date instance.
	 *
	 * @param  ExpressiveDate  $date
	 * @return bool
	 */
	public function lessThan( ExpressiveDate $date ): bool {
		return $this < $date;
	}

	/**
	 * Determine if date is greater than or equal to another Expressive Date instance.
	 *
	 * @param  ExpressiveDate  $date
	 * @return bool
	 */
	public function greaterOrEqualTo( ExpressiveDate $date ): bool {
		return $this >= $date;
	}

	/**
	 * Determine if date is less than or equal to another Expressive Date instance.
	 *
	 * @param  ExpressiveDate  $date
	 * @return bool
	 */
	public function lessOrEqualTo( ExpressiveDate $date ): bool {
		return $this <= $date;
	}

	/**
	 * Dynamically handle calls for date attributes and testers.
	 *
	 * @param  string  $method
	 * @param  array  $parameters
	 * @return mixed
	 */
	public function __call( $method, $parameters ) {
		if ( substr( $method, 0, 3 ) == 'get' || substr( $method, 0, 3 ) == 'set' ) {
			$attribute = substr( $method, 3 );
		} elseif ( substr( $method, 0, 2 ) == 'is' ) {
			$attribute = substr( $method, 2 );

			return $this->isDateAttribute( $attribute );
		}

		if ( ! isset( $attribute ) ) {
			throw new InvalidArgumentException( 'Could not dynamically handle method call [' . $method . ']' );
		}

		if ( substr( $method, 0, 3 ) == 'set' ) {
			return $this->setDateAttribute( $attribute, $parameters[0] );
		}

		// If not setting an attribute then we'll default to getting an attribute.
		return $this->getDateAttribute( $attribute );
	}

	/**
	 * Return the default date format when casting to string.
	 *
	 * @return string
	 */
	public function __toString(): string {
		return $this->getDefaultDate();
	}

	/**
	 * Determine if a given amount is a floating point number.
	 *
	 * @param  int|float  $amount
	 * @return bool
	 */
	protected function isFloat( $amount ): bool {
		return is_float( $amount ) && intval( $amount ) != $amount;
	}

	/**
	 * Return copy of expressive date object
	 *
	 * @return ExpressiveDate
	 */
	public function copy(): ExpressiveDate {
		return clone $this;
	}
}