PhutilLunarPhase.php
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	<?php

	/**
	* Compute the phase of the terran moon for a given epoch.
	*
	* $moon = new PhutilLunarPhase(time());
	* $moon->isFull();
	*/
	final class PhutilLunarPhase {

	private $epoch;

	public function __construct($epoch) {
	$this->epoch = $epoch;
	}

	private function getPhase() {
	// (Aug 11, 1999) A new moon.
	$new_moon_epoch = 934354800;

	// Number of seconds in the lunar phase.
	$phase_length = 2551442.8768992;

	return fmod($this->epoch - $new_moon_epoch, $phase_length) / $phase_length;
	}

	public function isFull() {
	return abs($this->getPhase() - 0.5) < 0.02;
	}

	public function isNew() {
	return $this->getPhase() < 0.02 \|\| $this->getPhase() > 0.98;
	}

	public function isWaxing() {
	return $this->getPhase() < 0.5;
	}

	public function isWaning() {
	return $this->getPhase() > 0.5;
	}

	}