Date repeater.
MONTH_SECONDS
30 * 24 * 60 * 60
$now :
$currentMonthStart :
width()
returns the width (in seconds or months) of this repeatable.
next( $pointer = 'future')
returns the next occurance of this repeatable.
this( $pointer = 'future')
__toString()
offset( $span, $amount, $pointer)