function Clock() {
                GcSpread.Sheets.SparklineEx.call(this);
            }
            Clock.prototype = new GcSpread.Sheets.SparklineEx();
            Clock.prototype.createFunction = function () {
                var func = new GcSpread.Sheets.Calc.Functions.Function("CLOCK", 1, 1);
                func.evaluate = function (args) {
                    return args[0];
                };
                return func;
            };
            Clock.prototype._drawCircle = function (context, centerX, centerY, radius) {
                context.beginPath();
                context.arc(centerX, centerY, radius, 0, Math.PI * 2, true);
                context.stroke();
            };
            Clock.prototype._drawCenter = function (context, centerX, centerY, radius) {
                context.beginPath();
                context.arc(centerX, centerY, radius, 0, Math.PI * 2, true);
                context.fill();
            };
            Clock.prototype._drawHand = function (context, centerX, centerY, loc, radius) {
                var angle = (Math.PI * 2) * (loc / 60) - Math.PI / 2;
                context.beginPath();
                context.moveTo(centerX, centerY);
                context.lineTo(centerX + Math.cos(angle) * radius, centerY + Math.sin(angle) * radius);
                context.stroke();
            };
            Clock.prototype._drawHands = function (context, value, centerX, centerY, radius) {
                var date = value, hour = date.getHours();
                hour = hour > 12 ? hour - 12 : hour;
                this._drawHand(context, centerX, centerY, hour * 5 + (date.getMinutes() / 60) * 5, radius / 2);
                this._drawHand(context, centerX, centerY, date.getMinutes(), radius * 3 / 4);
                context.strokeStyle = "red";
                this._drawHand(context, centerX, centerY, date.getSeconds(), radius * 3 / 4);

            };
            Clock.prototype._drawNumerals = function (context, centerX, centerY, radius) {
                var numerals = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12],
                    angle,
                    numeralWidth;
                if (radius > 0) {
                    numerals.forEach(function (numeral) {
                        angle = Math.PI / 6 * (numeral - 3);
                        numeralWidth = context.measureText(numeral).width;
                        context.beginPath();
                        context.fillText(numeral, centerX + Math.cos(angle) * radius + numeralWidth / 2, centerY + Math.sin(angle) * radius + numeralWidth / 2);
                    });
                }
            };
            Clock.prototype.paint = function (context, value, x, y, width, height) {
                if (!(value instanceof Date)) {
                    return;
                }
                var centerX = x + width / 2,
                    centerY = y + height / 2,
                    margin = 10,
                    padding = 10,
                    radius = Math.min(width, height) / 2 - margin;
                if (radius <= 0) {
                    return;
                }
                context.save();

                //draw circle
                this._drawCircle(context, centerX, centerY, radius);
                //draw center
                this._drawCenter(context, centerX, centerY, 3);
                //draw hands
                this._drawHands(context, value, centerX, centerY, radius);
                //draw numerals
                this._drawNumerals(context, centerX, centerY, radius - padding);

                context.restore();
            };
            spread.addSparklineEx(new Clock());

            var sheet = spread.getActiveSheet();

            var style = new GcSpread.Sheets.Style();
            style.hAlign = GcSpread.Sheets.HorizontalAlign.center;
            style.vAlign = GcSpread.Sheets.VerticalAlign.center;
            sheet.setDefaultStyle(style);
            sheet.getCell(0, 1).value("Universal Time").font("20px Arial");
            sheet.setValue(1, 0, "Beijing");
            sheet.setValue(1, 1, "Tokyo");
            sheet.setValue(1, 2, "New York");
            sheet.setFormula(2, 0, '=CLOCK(A4)');
            sheet.setFormula(2, 1, '=CLOCK(B4)');
            sheet.setFormula(2, 2, '=CLOCK(C4)');
            sheet.getRow(3).formatter("hh:mm:ss tt");
            sheet.setRowHeight(0, 50);
            sheet.setRowHeight(2, 200);
            sheet.setColumnWidth(0, 200);
            sheet.setColumnWidth(1, 200);
            sheet.setColumnWidth(2, 200);
            function updateTime() {
                var now = new Date();
                var utcNow = new Date(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate(), now.getUTCHours(), now.getUTCMinutes(), now.getUTCSeconds(), now.getUTCMilliseconds());
                sheet.setValue(3, 0, new Date(utcNow.setHours(utcNow.getHours() + 8)));//+8
                sheet.setValue(3, 1, new Date(utcNow.setHours(utcNow.getHours() + 1)));//+9
                sheet.setValue(3, 2, new Date(utcNow.setHours(utcNow.getHours() - 14)));//-5
            }
            setInterval(updateTime, 1000);
            updateTime();