Draw clock (LWJGL 2 + Slick 2D)

Clock.java

package me.superblaubeere27;

import org.lwjgl.LWJGLException;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import org.lwjgl.opengl.GL11;
import org.lwjgl.opengl.PixelFormat;
import org.newdawn.slick.TrueTypeFont;

import java.awt.*;
import java.sql.Time;
import java.text.SimpleDateFormat;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.util.Calendar;
import java.util.Date;

import static java.lang.Math.cos;
import static java.lang.StrictMath.sin;
import static org.lwjgl.opengl.GL11.glBegin;


public class Clock {
    private static final double TRIANGLE_AMOUNT = 40;
    private TrueTypeFont font;
    private static final SimpleDateFormat TIME_FORMATTER = new SimpleDateFormat("HH:mm:ss");
    private static final SimpleDateFormat DATE_FORMATTER = new SimpleDateFormat("dd/MM/yyyy");

    private void start() {
        try {
            Display.setDisplayMode(new DisplayMode(1280, 720));
            for (DisplayMode availableDisplayMode : Display.getAvailableDisplayModes()) {
                if (availableDisplayMode.getWidth() == 1920 && availableDisplayMode.getHeight() == 1080 && availableDisplayMode.isFullscreenCapable()) {
                    Display.setDisplayMode(availableDisplayMode);
                    Display.setFullscreen(true);
                    break;
                }
            }
            Display.setVSyncEnabled(true);
            Display.setResizable(true);
            Display.setTitle("Clock");
            Display.create(new PixelFormat(0, 8, 0, 16));
        } catch (LWJGLException e) {
            e.printStackTrace();
            System.exit(-1);
        }

        // init OpenGL
        initGL();

        init();

        while (!Display.isCloseRequested()) {
            // Clear the screen and depth buffer
            GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT);

            render();

            Display.update();

            update();
        }

        Display.destroy();
    }

    private void initGL() {
        GL11.glEnable(GL11.GL_TEXTURE_2D);
        GL11.glShadeModel(GL11.GL_SMOOTH);
        GL11.glDisable(GL11.GL_DEPTH_TEST);
        GL11.glDisable(GL11.GL_LIGHTING);

        GL11.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        GL11.glClearDepth(1);

        GL11.glEnable(GL11.GL_BLEND);
        GL11.glBlendFunc(GL11.GL_SRC_ALPHA, GL11.GL_ONE_MINUS_SRC_ALPHA);

        GL11.glViewport(0, 0, Display.getWidth(), Display.getHeight());
        GL11.glMatrixMode(GL11.GL_MODELVIEW);

        GL11.glMatrixMode(GL11.GL_PROJECTION);
        GL11.glLoadIdentity();
        GL11.glOrtho(0, Display.getWidth(), Display.getHeight(), 0, 1, -1);
        GL11.glMatrixMode(GL11.GL_MODELVIEW);
    }

    private void init() {
        Font awtFont = new Font("Bebas Neue Bold", Font.PLAIN, 40);
        font = new TrueTypeFont(awtFont, true);
    }

    private void update() {

    }

    private void render() {
        GL11.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        GL11.glPushMatrix();

        double radius = Display.getHeight() * 0.39;

        LocalDateTime now = LocalDateTime.now();

        GL11.glTranslated(Display.getWidth() / 2.0, Display.getHeight() / 2.0 - font.getHeight(), 0);
        GL11.glEnable(GL11.GL_TEXTURE_2D);

        Date today = Calendar.getInstance().getTime();
        String time = TIME_FORMATTER.format(today);

        font.drawString(-font.getWidth(time) / 2.0f, (float) (radius + 5.0), time);

        time = DATE_FORMATTER.format(today);

        font.drawString(-font.getWidth(time) / 2.0f, (float) (radius + 5.0 + font.getHeight()), time);

        GL11.glDisable(GL11.GL_TEXTURE_2D);
        GL11.glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
        GL11.glLineWidth(1.0f);


        drawCircle(0, 0, 8, true);
        drawCircle(0, 0, radius, false);

        double seconds = (now.getSecond() + System.currentTimeMillis() % 1000 / 1000.0);
        double minutes = (now.getMinute() + seconds / 60.0);
        double hours = (now.getHour() + minutes / 60.0);

        GL11.glLineWidth(1.0f);
        drawHand(seconds / 60.0 * 100.0, radius);
        GL11.glLineWidth(4.0f);
        drawHand(minutes / 60.0 * 100.0, radius * 0.75);
        GL11.glLineWidth(8.0f);
        drawHand(hours / 12.0 * 100.0, radius * 0.5);

        GL11.glPopMatrix();
    }

    private void drawHand(double percentage, double radius) {
        double conv = convertPercentage(percentage);

        GL11.glBegin(GL11.GL_LINES);


        GL11.glVertex2d(0, 0);
        GL11.glVertex2d(-radius * Math.sin(conv), radius * Math.cos(conv));

        GL11.glEnd();
    }

    private double convertPercentage(double percentage) {
        return percentage / 100.0 * Math.PI * 2.0 + Math.PI;
    }

    private static void drawCircle(double x, double y, double radius, boolean fill) {
        int i;

        double twicePi = 2.0 * Math.PI;

        int triageAmount = Math.max((int) (radius * Math.PI * 2 / 15), 10);

        glBegin(fill ? GL11.GL_TRIANGLE_FAN : GL11.GL_LINE_STRIP);

        for (i = 0; i <= triageAmount; i++) {
            GL11.glVertex2d(
                    x + (radius * cos(i * twicePi / triageAmount)),
                    y + (radius * sin(i * twicePi / triageAmount))
            );
        }

        GL11.glEnd();
    }

    public static void main(String[] argv) {
        Clock quadExample = new Clock();
        quadExample.start();
    }
}