/**
 * Get a string describing the difference between two timestamps.
 *
 * @var time Date object to retrieve relative description string of
 *
 * @return string indicating how far in the past or future the date is
 */
function getTimeDiff(time)
{
 
	var now = new Date();
	var diff = now.getTime() - time.getTime();
 
	var timeDiff = getTimeDiffDescription(diff, 'day', 86400000);
	if (!timeDiff) {
		timeDiff = getTimeDiffDescription(diff, 'hour', 3600000);
		if (!timeDiff) {
			timeDiff = getTimeDiffDescription(diff, 'minute', 60000);
			if (!timeDiff) {
				timeDiff = getTimeDiffDescription(diff, 'second', 60);
				if (!timeDiff) {
					timeDiff = 'just now';
				}
			}
		}
	}
 
	return timeDiff;
 
}
 
/**
 * Get a string describing the difference between two timestamps,
 * based on unit of time. Run sequentially starting from the greatest
 * unit and stopping once this function doesn't return null.
 *
 * @var diff current time (in millisec since 1970) minus time to compare to.
 *           e.g., (new DateTime()).getTime() - someOtherTime.getTime()
 * @var unit Time description to place in a string. e.g., 'hour'
 * @var timeDivisor Number to divide into milliseconds to get the value
 *                  described by the unit. e.g., 60*60*1000 for 'hour'
 *
 * @return A string representing the difference between the given time
 *         and now, if there is a difference for the given unit of time.
 *         null is returned if they're the same (e.g., provided time falls
 *         on today when unit = 'day')
 */
function getTimeDiffDescription(diff, unit, timeDivisor)
{
 
	var unitAmount = (diff / timeDivisor).toFixed(0);
	if (unitAmount > 0) {
		return unitAmount + ' ' + unit + (unitAmount == 1 ? '': 's') + ' ago';
	} else if (unitAmount < 0) {
		return 'in ' + Math.abs(unitAmount) + ' ' + unit + (unitAmount == 1 ? '' : 's');
	} else {
		return null;
	}
 
}