jquery-ui-datespinner.js

/**
 * datespinner "yyyy/mm/dd"
 */
$.widget( "ui.datespinner", $.ui.spinner, {
    options: { step: 60*60*24*1000, page: 60*60*24*1000 },
    _parse: function( value ) {
        if ( typeof value === "string" ) {
            if ( Number( value ) == value ) {
                return Number( value );
            }
            if(value == '') {
                return null;
            }
            var t = value.split('/');
            if(t.length != 3) {
                return null;
            }
            var y = Number(t[0]);
            var m = Number(t[1]);
            var d = Number(t[2]);
            var dt = new Date(y, m - 1, d, 0, 0, 0, 0);
            var time = dt.getTime();
            return time;
        }
        return value;
    },
    _format: function( value ) {
        if(value == null) {
            return '';
        }
        var dt = new Date();
        dt.setTime(Number(value));
        var y = dt.getFullYear();
        var mm = "00" + (dt.getMonth() + 1);
        var dd = "00" + dt.getDate();
        var s = y + '/' + mm.substring(mm.length - 2)
                  + '/' + dd.substring(dd.length - 2);
        return s;
    }
});