var RETRY = 3;
var time, time2;

Number.prototype.toString2 = function () {
    var str = "";
    if (this < 10) str += "0";
    str += this;
    return str;
}

Date.prototype.toTimeString = function () {
    return "" +
        this.getFullYear() + (this.getMonth() + 1).toString2() +
        this.getDate().toString2() + this.getHours().toString2() +
        this.getMinutes().toString2();
}

function setImg(time) {
    var src;
    src = "http://www.jma.go.jp/jp/radnowc/imgs/radar/215/" +
        time.toTimeString() + "-00.png";
    radar.src = src;
    rtime.src = src;
}

function init() {
    var min;
    time = new Date();
    min = Math.floor(time.getMinutes() / 5) * 5;
    time.setMinutes(min);
    time.setSeconds(0);
    time.setMilliseconds(0);
    time2 = new Date(time.getTime() - RETRY * 5 * 60000);
    setImg(time);
}

function imgError() {
    time.setTime(time.getTime() - 5 * 60000);
    if (time.getTime() > time2.getTime()) {
        setImg(time);
    }
}