If you mean minus one month, then you could do:
$date = "2014-3-19 00:00:00";
$newDate = date("Y, n, j, H, i", strtotime('-1 month', strtotime($date)));
And 2014, 1, 19, 00
will be 2013, 12, 19, 00
but not 2014, 0, 19, 00
.
Update:
You want to pass a date to the jQuery plugin(jquery.magicbusmultimedia.net).
The plugin only ask you to pass a javascript Date object.
So you could do:
$('#myCounter').mbComingsoon(new Date(<?php echo strtotime($date); ?> * 1000));