话不多说，咱们先看效果。

分级结构：

Cale_Main部分

/*
 *所使用的环境是IDE,java 11 版本,以下会存在原子类型。
 *java.concurrent.atomic 包含了许多有用的类实现原子操作。
 * 原子操作是多个线程同时执行，确保其是安全的，且并不需要synchronized 关键字。
 * 这里使用了 AtomicInteger、AtomicReference，这里主要演示AtomicInteger类。
 * 这些指令通常比同步块要快。
 * 所以在只需要并发修改单个可变变量的情况下，
 * 优先使用原子类，而不是使用锁机制实现。
 * 这里使用原子类型的原因是因为IDE的自动提示功能。
 *
 */


package work2;


import javafx.application.Application;
import javafx.scene.Scene;
import javafx.stage.Stage;


public class Cale_Main extends Application {

    public static void main(String[] args) {
        Application.launch(args);
    }

    public void start(Stage primaryStage) {
        primaryStage.setResizable(false);
        Cale_Pane cale = new Cale_Pane();
        Scene scene = new Scene(cale, 860, 340);
        primaryStage.setTitle("我的日历");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
}

Cale_Pane部分

package work2;


import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.*;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.scene.text.FontPosture;
import javafx.scene.text.FontWeight;
import javafx.scene.text.Text;
import javafx.util.Duration;

import java.util.Calendar;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;

import static javafx.geometry.HPos.CENTER;
import static javafx.geometry.HPos.RIGHT;

class Cale_Pane extends Pane {
    private int year;
    private int final_year;
    private int month;
    private int final_month;
    private int day;
    private int final_day;
    private int firstDayOfWeek;
    private int totalDayOfMonth;
    private String NowTime;
    private AtomicReference<Text> text1 = new AtomicReference<>(new Text());
    //set week label
    private Label[] week_label = new Label[7];
    // set cale[8][7]
    private Label[][] cale_label = new Label[6][7];
    //set_row and col
    private AtomicInteger next_month_rowIndex = new AtomicInteger();
    private AtomicInteger next_month_columnIndex = new AtomicInteger();
    private AtomicInteger tmp_day = new AtomicInteger(1);

    Cale_Pane() {

        Calendar calendar = Calendar.getInstance();
        year = calendar.get(Calendar.YEAR);
        month = calendar.get(Calendar.MONTH) + 1;
        day = calendar.get(Calendar.DAY_OF_MONTH);
        totalDayOfMonth = calendar.getActualMaximum(Calendar.DATE);
        calendar.set(Calendar.DAY_OF_MONTH, 1);
        firstDayOfWeek = calendar.get(Calendar.DAY_OF_WEEK) - 1;
        paint();
    }

    private void paint() {
        Now_Time cp = new Now_Time();

        final_year = year;
        final_month = month;
        final_day = day;

        BorderPane bp = new BorderPane();
        GridPane gridPane = new GridPane();
        bp.setTop(gridPane);

        String[] week = new String[]{"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
        gridPane.setPadding(new Insets(30, 30, 10, 10));
        text1.get().setText(year + "年" + month + "月");
        text1.get().setStroke(Color.GREEN);
        text1.get().setFont(Font.font(20));

        gridPane.setAlignment(Pos.CENTER);
        gridPane.add(text1.get(), 0, 0);
        GridPane.setColumnSpan(text1.get(), 7);
        GridPane.setHalignment(text1.get(), CENTER);

        //set week
        for (int i = 0; i < 7; i++) {
            week_label[i] = new Label(week[i]);
            week_label[i].setFont(Font.font("微软雅黑", FontWeight.BOLD, 20));
            if (i == 0 || i == 6) week_label[i].setTextFill(Color.RED);
            GridPane.setColumnSpan(week_label[i], 2);
            gridPane.add(week_label[i], i, 1);
            gridPane.getColumnConstraints().add(new ColumnConstraints(30));
            GridPane.setHalignment(week_label[i], HPos.LEFT);
        }
//        System.out.println(return_last_month_days());


        //judge and set last month
        if (firstDayOfWeek != 7) {
            for (int j = 0; j < firstDayOfWeek; j++) {
                cale_label[0][j] = new Label(j + return_last_month_days() - firstDayOfWeek + 1 + "");
                cale_label[0][j].setFont(Font.font("Times New Roman", FontWeight.BOLD, FontPosture.ITALIC, 20));
                cale_label[0][j].setTextFill(Color.GRAY);
                gridPane.add(cale_label[0][j], j, 2);
                GridPane.setHalignment(cale_label[0][j], RIGHT);
            }
        }
        //set now month

        for (int j = 0; j < totalDayOfMonth; j++) {

            int k = firstDayOfWeek + j;

            cale_label[k / 7][k % 7] = new Label(j + 1 + "");
            cale_label[k / 7][k % 7].setFont(Font.font("Times New Roman", FontWeight.BOLD, 20));
//            System.out.println(firstDayOfWeek);
            if ((k % 7 == 0) || (k % 7 == 6)) cale_label[k / 7][k % 7].setTextFill(Color.RED);
            if (j + 1 == final_day && final_month == month && final_year == year) {
                cale_label[k / 7][k % 7].setFont(Font.font("Cooper Black", FontWeight.BOLD, 20));
                cale_label[k / 7][k % 7].setTextFill(Color.CORAL);
            }
            gridPane.add(cale_label[k / 7][k % 7], k % 7, 2 + k / 7);
            next_month_rowIndex.set(2 + k / 7);
            next_month_columnIndex.set(k % 7);
            GridPane.setHalignment(cale_label[k / 7][k % 7], RIGHT);
        }

        //set next month

        //!!! having a bug,it's the next_month_columnIndex and rowIndex
        next_month_columnIndex.set(((next_month_columnIndex.get() + 1) % 7));
        next_month_rowIndex.addAndGet((next_month_columnIndex.get() == 0 ? 1 : 0));
        while (!(next_month_columnIndex.get() == 0 && next_month_rowIndex.get() == 8)) {

            cale_label[next_month_rowIndex.get() - 2][next_month_columnIndex.get()] = new Label(tmp_day + "");
            cale_label[next_month_rowIndex.get() - 2][next_month_columnIndex.get()].setFont(Font.font("Times New Roman", FontWeight.BOLD, FontPosture.ITALIC, 20));
            cale_label[next_month_rowIndex.get() - 2][next_month_columnIndex.get()].setTextFill(Color.GRAY);

            gridPane.add(cale_label[next_month_rowIndex.get() - 2][next_month_columnIndex.get()], next_month_columnIndex.get() % 7, next_month_rowIndex.get());

            GridPane.setHalignment(cale_label[next_month_rowIndex.get() - 2][next_month_columnIndex.get()], RIGHT);
            tmp_day.getAndIncrement();
            next_month_columnIndex.set((next_month_columnIndex.incrementAndGet()) % 7);
            //the key
            next_month_rowIndex.addAndGet((next_month_columnIndex.get() == 0 ? 1 : 0));
        }


        //GET NEW
        GridPane gridPane2 = new GridPane();
        Button setting = new Button("Setting");
        Button Prior = new Button("Prior");
        Button Next = new Button("Next");
        Button Now = new Button("Now");

        GridPane.setColumnSpan(setting, 4);

        GridPane.setColumnSpan(Prior, 4);
//        GridPane.setHalignment(Prior, CENTER_LEFT);
        GridPane.setColumnSpan(Next, 4);
//        GridPane.setHalignment(Next, CENTER);
        GridPane.setColumnSpan(Now, 4);
//        GridPane.setHalignment(Now, CENTER);
        gridPane2.add(setting, 2, 1);
        gridPane2.add(Prior, 8, 1);
        gridPane2.add(Next, 16, 1);
        gridPane2.add(Now, 24, 1);
        //gridPane2.setAlignment(Pos.CENTER);

        //set pane2 gap
        gridPane2.setHgap(28);
        gridPane2.setVgap(0);
        //set pane gap
        gridPane.setHgap(94);
        gridPane.setVgap(5);

        bp.setBottom(gridPane2);


        //点击prior
        Prior.setOnAction(e -> {
            //to clear
            //gridPane.getChildren().clear();
            //init
            to_add_month(-2);
            to_update_information();
        });

        //点击Next
        Next.setOnAction(e -> {
            to_add_month(0);
            to_update_information();
        });

        //点击Now
        Now.setOnAction(e -> {
            Calendar set_calendar = Calendar.getInstance();
            set_calendar.set(final_year, final_month - 1, final_day);
            year = set_calendar.get(Calendar.YEAR);
            month = set_calendar.get(Calendar.MONTH) + 1;
            day = set_calendar.get(Calendar.DAY_OF_MONTH);
            totalDayOfMonth = set_calendar.getActualMaximum(Calendar.DATE);
            set_calendar.set(Calendar.DAY_OF_MONTH, 1);
            firstDayOfWeek = set_calendar.get(Calendar.DAY_OF_WEEK) - 1;
            to_update_information();
        });

        setting.setOnAction(e -> {
            Setting_date set = new Setting_date(year, month);
            set.show();
            //System.out.println(set.getTo_return_month());
            int tmp_year = set.getTo_return_year();
            int tmp_month = set.getTo_return_month();
            Calendar set_calendar = Calendar.getInstance();
            set_calendar.set(tmp_year, tmp_month - 1, final_day);
            year = set_calendar.get(Calendar.YEAR);
            month = set_calendar.get(Calendar.MONTH) + 1;
            day = set_calendar.get(Calendar.DAY_OF_MONTH);
            totalDayOfMonth = set_calendar.getActualMaximum(Calendar.DATE);
            set_calendar.set(Calendar.DAY_OF_MONTH, 1);
            firstDayOfWeek = set_calendar.get(Calendar.DAY_OF_WEEK) - 1;
            to_update_information();
        });


        StackPane nt = new StackPane();
        EventHandler<ActionEvent> eventHandler = e -> {
            nt.getChildren().clear();
            NowTime = cp.setCurrentTime();
            Text tt = new Text(NowTime);
            tt.setFont(Font.font("Times New Roman", 20));
            nt.getChildren().add(tt);
        };
        Timeline animation = new Timeline(
                new KeyFrame(Duration.millis(1000), eventHandler));
        animation.setCycleCount(Timeline.INDEFINITE);
        animation.play();

        gridPane2.add(nt, 14, 0);
//        gridPane.add(sp, 14, 4);
        nt.setAlignment(Pos.BOTTOM_CENTER);
        //bp.setRight(sp);
//        sp.setAlignment(Pos.BOTTOM_RIGHT);
        getChildren().add(bp);
        Start_Tishi.display("起始窗口", "Today is " +
                year + " year " + month + " month " + day + " day "
                + week[day % 7]);
    }

    private void to_add_month(int add) {
        Calendar set_calendar = Calendar.getInstance();
        set_calendar.set(year, month + add, day);
        year = set_calendar.get(Calendar.YEAR);
        month = set_calendar.get(Calendar.MONTH) + 1;
        day = set_calendar.get(Calendar.DAY_OF_MONTH);
        totalDayOfMonth = set_calendar.getActualMaximum(Calendar.DATE);
        set_calendar.set(Calendar.DAY_OF_MONTH, 1);
        firstDayOfWeek = set_calendar.get(Calendar.DAY_OF_WEEK) - 1;
    }

    private int return_last_month_days() {
        Calendar last_month;
        last_month = Calendar.getInstance();
        last_month.set(year, month - 1 - 1, day);
        return last_month.getActualMaximum(Calendar.DATE);
    }

    private void to_update_information() {
        next_month_rowIndex.set(0);
        next_month_columnIndex.set(0);
        text1.get().setText(year + "年" + month + "月");

        // set last month
        if (firstDayOfWeek != 7) {
            for (int j = 0; j < firstDayOfWeek; j++) {
                cale_label[0][j].setText(j + return_last_month_days() - firstDayOfWeek + 1 + "");
                cale_label[0][j].setFont(Font.font("Times New Roman", FontWeight.BOLD, FontPosture.ITALIC, 20));
                cale_label[0][j].setTextFill(Color.GRAY);
            }

        }

        //set now month
        for (int j = 0; j < totalDayOfMonth; j++) {
            int k = firstDayOfWeek + j;
            cale_label[k / 7][k % 7].setText(j + 1 + "");
            if (j + 1 == final_day && final_month == month && final_year == year) {
                if ((k % 7 == 0) || (k % 7 == 6)) cale_label[k / 7][k % 7].setTextFill(Color.RED);
                cale_label[k / 7][k % 7].setFont(Font.font("Cooper Black", FontWeight.BOLD, 20));
                cale_label[k / 7][k % 7].setTextFill(Color.CORAL);
            } else {
                cale_label[k / 7][k % 7].setFont(Font.font("Times New Roman", FontWeight.BOLD, 20));
                cale_label[k / 7][k % 7].setTextFill(Color.BLACK);
                if ((k % 7 == 0) || (k % 7 == 6)) cale_label[k / 7][k % 7].setTextFill(Color.RED);
            }
            next_month_rowIndex.set(2 + k / 7);
            next_month_columnIndex.set(k % 7);
        }

        //set next month
        tmp_day.set(1);
        //!!! having a bug,it's the next_month_columnIndex and rowIndex
        next_month_columnIndex.set(((next_month_columnIndex.get() + 1) % 7));
        next_month_rowIndex.addAndGet((next_month_columnIndex.get() == 0 ? 1 : 0));
        while (!(next_month_columnIndex.get() == 0 && next_month_rowIndex.get() == 8)) {

            cale_label[next_month_rowIndex.get() - 2][next_month_columnIndex.get()].setText(tmp_day + "");
            cale_label[next_month_rowIndex.get() - 2][next_month_columnIndex.get()].setFont(Font.font("Times New Roman", FontWeight.BOLD, FontPosture.ITALIC, 20));
            cale_label[next_month_rowIndex.get() - 2][next_month_columnIndex.get()].setTextFill(Color.GRAY);
            tmp_day.getAndIncrement();
            next_month_columnIndex.set((next_month_columnIndex.incrementAndGet()) % 7);
            //the key
            next_month_rowIndex.addAndGet((next_month_columnIndex.get() == 0 ? 1 : 0));
        }
    }
}

Now_Time部分

package work2;


import java.util.Calendar;
import java.util.GregorianCalendar;

import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Line;

public class Now_Time extends Pane {
    private int hour;
    private int minute;
    private int second;

    Now_Time() {
        setCurrentTime();
    }

    String setCurrentTime() {
        String str1, str2, str3;
        Calendar calendar = new GregorianCalendar();
        this.hour = calendar.get(Calendar.HOUR_OF_DAY);
        this.minute = calendar.get(Calendar.MINUTE);
        this.second = calendar.get(Calendar.SECOND);
        str1 = String.valueOf(hour);
        str2 = String.valueOf(minute);
        str3 = String.valueOf(second);
        if (hour < 10) {
            str1 = "0" + hour;
        }
        if (minute < 10) {
            str2 = "0" + minute;
        }
        if (second < 10) {
            str3 = "0" + second;
        }
        paint();
        return str1 + " : " + str2 + " : " + str3;
    }

    protected void paint() {
        getChildren().clear();
        double w = 200;
        double h = 200;
        double clockRadius = Math.min(w, h) * 0.8 * 0.5;
        double centerX = w / 2;
        double centerY = h / 2;
        double sLength = clockRadius * 0.8;
        double secondX = centerX + sLength * Math.sin(second * (2 * Math.PI) / 60);
        double secondY = centerY - sLength * Math.cos(second * (2 * Math.PI) / 60);
        Line sLine = new Line(centerX, centerY, secondX, secondY);
        sLine.setStroke(Color.RED);
        double mLength = clockRadius * 0.65;
        double minuteX = centerX + mLength * Math.sin(minute * (2 * Math.PI) / 60);
        double minuteY = centerY - mLength * Math.cos(minute * (2 * Math.PI) / 60);
        Line mLine = new Line(centerX, centerY, minuteX, minuteY);
        mLine.setStroke(Color.BLUE);
        double hLength = clockRadius * 0.5;
        double hourX = centerX + hLength * Math.sin(hour * (2 * Math.PI) / 12);
        double hourY = centerY - hLength * Math.cos(hour * (2 * Math.PI) / 12);
        Line hLine = new Line(centerX, centerY, hourX, hourY);
        mLine.setStroke(Color.GREEN);
        getChildren().addAll(sLine, mLine, hLine);
    }
}

Setting_date部分

package work2;

import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ListView;
import javafx.scene.control.SelectionMode;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.stage.Modality;
import javafx.stage.Stage;

class Setting_date {

    private int to_return_year;
    private int to_return_month;
    private int year;
    private int month;
    Setting_date() {
    }

    Setting_date(int year, int month) {
        this.to_return_year = this.year = year;
        this.to_return_month = this.month = month;
    }

    void show(){
        Stage stage = new Stage();
        stage.setResizable(false);
        stage.setTitle("Setting");
        //modality要使用Modality.APPLICATION_MODEL
        stage.initModality(Modality.APPLICATION_MODAL);
        stage.setMinWidth(300);
        stage.setMinHeight(250);


        BorderPane bp = new BorderPane();

        Label label_year = new Label("Year");
        Label label_month = new Label("month");
        label_year.setTextFill(Color.rgb(100, 107, 48));
        label_year.setFont(Font.font("Times New Roman", 26));
        label_month.setTextFill(Color.rgb(100, 107, 48));
        label_month.setFont(Font.font("Times New Roman", 26));

        GridPane gp = new GridPane();
        gp.add(label_year, 0, 0);
        gp.add(label_month, 2, 0);
        gp.setHgap(40);
        gp.setAlignment(Pos.CENTER);

        ObservableList<Integer> year_12 = FXCollections.observableArrayList();
        for (int i = year + 3; i >= year; i--)
            year_12.add(i);
        for (int i = year - 1; i >= year - 100; i--)
            year_12.add(i);
        ListView<Integer> left_year = new ListView<>(year_12);
        left_year.getSelectionModel().setSelectionMode(SelectionMode.SINGLE);
        left_year.setPrefSize(150, 200);
        left_year.getSelectionModel().selectedItemProperty().addListener(ov->{
            //System.out.println(left_year.getSelectionModel().getSelectedIndices());
            //System.out.println(left_year.getSelectionModel().getSelectedItem());
            this.to_return_year = left_year.getSelectionModel().getSelectedItem();
        });

        ObservableList<Integer> month_12 = FXCollections.observableArrayList(1,2,3,4,5,6,7,8,9,10,11,12);
        ListView<Integer> right_month = new ListView<>(month_12);
        right_month.getSelectionModel().setSelectionMode(SelectionMode.SINGLE);
        right_month.setPrefSize(150, 200);
        right_month.getSelectionModel().selectedItemProperty().addListener(ov -> {
            this.to_return_month = right_month.getSelectionModel().getSelectedItem();
        });


        Button button = new Button("关闭设置");
        button.setOnAction(e -> stage.close());

        button.setTextFill(Color.rgb(222,156,83));
        button.setFont(Font.font("微软雅黑", 16));
        GridPane gp2 = new GridPane();
        gp2.add(button,0,0);
        gp2.setAlignment(Pos.CENTER);

        bp.setTop(gp);
        bp.setLeft(left_year);
        bp.setRight(right_month);
        bp.setBottom(gp2);

        Scene scene = new Scene(bp);
        stage.setScene(scene);
        //使用showAndWait()先处理这个窗口，而如果不处理，main中的那个窗口不能响应
        stage.showAndWait();
    }

    int getTo_return_year() {
        return to_return_year;
    }

    int getTo_return_month() {
        return to_return_month;
    }


}

Start_Tishi部分

package work2;

import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.StackPane;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.text.Font;
import javafx.scene.text.Text;
import javafx.stage.Modality;
import javafx.stage.Stage;
import javafx.util.Duration;

class Start_Tishi {
    private static String NowTime;
    static void display(String title, String message){
        Stage window = new Stage();
        window.setResizable(false);
        window.setTitle(title);
        //modality要使用Modality.APPLICATION_MODEL
        window.initModality(Modality.APPLICATION_MODAL);
        window.setMinWidth(600);
        window.setMinHeight(250);
        Button button = new Button("欢迎您的使用");
        button.setOnAction(e -> window.close());
        button.setTextFill(Color.rgb(222,156,83));
        button.setFont(Font.font("微软雅黑", 18));
        Label label = new Label(message);
        label.setTextFill(Color.rgb(100, 107, 48));
        label.setFont(Font.font("Times New Roman", 26));
        VBox layout = new VBox(10);
        StackPane nt = new StackPane();
        Now_Time cp = new Now_Time();
        EventHandler<ActionEvent> eventHandler = e -> {
            nt.getChildren().clear();
            NowTime = (String) cp.setCurrentTime();
            Text tt = new Text(NowTime);
            tt.setFont(Font.font("Times New Roman", 20));
            nt.getChildren().add(tt);
        };
        Timeline animation = new Timeline(
                new KeyFrame(Duration.millis(1000), eventHandler));
        animation.setCycleCount(Timeline.INDEFINITE);
        animation.play();
        layout.getChildren().addAll(label , nt, button);
        layout.setAlignment(Pos.CENTER);
        Scene scene = new Scene(layout);
        window.setScene(scene);
        //使用showAndWait()先处理这个窗口，而如果不处理，main中的那个窗口不能响应
        window.showAndWait();
    }
}