Java 8 Date and Time API Tutorial with Practical Examples

Java 8 introduced a modern date‑time API that replaces the mutable and non‑thread‑safe java.util.Date and SimpleDateFormat with immutable, thread‑safe classes in the java.time package, following ISO standards and offering clearer concepts like Instant , Duration , LocalDate , LocalTime , ZonedDateTime , and more.

Key Classes

Instant : represents a point in time.

LocalDate : date without time, e.g., birthdays.

LocalTime : time without date.

LocalDateTime : date and time without zone.

ZonedDateTime : full date‑time with zone information.

The API also adds ZoneOffset , ZoneId , and DateTimeFormatter for easier time‑zone handling and formatting.

Practical Examples

1. Get Current Date

//获取今天的日期
public void getCurrentDate(){
    LocalDate today = LocalDate.now();
    System.out.println("Today's Local date : " + today);
    Date date = new Date();
    System.out.println(date);
}

2. Extract Year, Month, Day

//获取年、月、日信息
public void getDetailDate(){
    LocalDate today = LocalDate.now();
    int year = today.getYear();
    int month = today.getMonthValue();
    int day = today.getDayOfMonth();
    System.out.printf("Year : %d  Month : %d  day : %d%n", year, month, day);
}

3. Create Specific Date

//处理特定日期
public void handleSpecilDate(){
    LocalDate dateOfBirth = LocalDate.of(2018, 01, 21);
    System.out.println("The specil date is : " + dateOfBirth);
}

4. Compare Two Dates

//判断两个日期是否相等
public void compareDate(){
    LocalDate today = LocalDate.now();
    LocalDate date1 = LocalDate.of(2018, 01, 21);
    if(date1.equals(today)){
        System.out.printf("TODAY %s and DATE1 %s are same date %n", today, date1);
    }
}

5. Handle Recurring Events (Birthday)

//处理周期性的日期
public void cycleDate(){
    LocalDate today = LocalDate.now();
    LocalDate dateOfBirth = LocalDate.of(2018, 01, 21);
    MonthDay birthday = MonthDay.of(dateOfBirth.getMonth(), dateOfBirth.getDayOfMonth());
    MonthDay currentMonthDay = MonthDay.from(today);
    if(currentMonthDay.equals(birthday)){
        System.out.println("Many Many happy returns of the day !!");
    } else {
        System.out.println("Sorry, today is not your birthday");
    }
}

6. Get Current Time

//获取当前时间
public void getCurrentTime(){
    LocalTime time = LocalTime.now();
    System.out.println("local time now : " + time);
}

7. Add Hours to Time

//增加小时
public void plusHours(){
    LocalTime time = LocalTime.now();
    LocalTime newTime = time.plusHours(2); // 增加两小时
    System.out.println("Time after 2 hours : " + newTime);
}

8. Calculate Date One Week Later

//如何计算一周后的日期
public void nextWeek(){
    LocalDate today = LocalDate.now();
    LocalDate nextWeek = today.plus(1, ChronoUnit.WEEKS);
    System.out.println("Today is : " + today);
    System.out.println("Date after 1 week : " + nextWeek);
}

9. Calculate One Year Before/After

//计算一年前或一年后的日期
public void minusDate(){
    LocalDate today = LocalDate.now();
    LocalDate previousYear = today.minus(1, ChronoUnit.YEARS);
    System.out.println("Date before 1 year : " + previousYear);
    LocalDate nextYear = today.plus(1, ChronoUnit.YEARS);
    System.out.println("Date after 1 year : " + nextYear);
}

10. Use Clock for Timestamps

//使用Java 8的Clock时钟类
public void clock(){
    Clock clock = Clock.systemUTC();
    System.out.println("Clock : " + clock);
    Clock defaultClock = Clock.systemDefaultZone();
    System.out.println("Clock : " + clock);
}

11. Compare Dates with isBefore / isAfter

//如何用Java判断日期是早于还是晚于另一个日期
public void isBeforeOrIsAfter(){
    LocalDate today = LocalDate.now();
    LocalDate tomorrow = LocalDate.of(2018, 1, 29);
    if(tomorrow.isAfter(today)){
        System.out.println("Tomorrow comes after today");
    }
    LocalDate yesterday = today.minus(1, ChronoUnit.DAYS);
    if(yesterday.isBefore(today)){
        System.out.println("Yesterday is day before today");
    }
}

12. Time‑Zone Handling

//获取特定时区下面的时间
public void getZoneTime(){
    ZoneId america = ZoneId.of("America/New_York");
    LocalDateTime localtDateAndTime = LocalDateTime.now();
    ZonedDateTime dateAndTimeInNewYork = ZonedDateTime.of(localtDateAndTime, america);
    System.out.println("现在的日期和时间在特定的时区 : " + dateAndTimeInNewYork);
}

13. YearMonth for Fixed Dates (e.g., Credit Card Expiry)

//使用 YearMonth类处理特定的日期
public void checkCardExpiry(){
    YearMonth currentYearMonth = YearMonth.now();
    System.out.printf("Days in month year %s: %d%n", currentYearMonth, currentYearMonth.lengthOfMonth());
    YearMonth creditCardExpiry = YearMonth.of(2028, Month.FEBRUARY);
    System.out.printf("Your credit card expires on %s %n", creditCardExpiry);
}

14. Leap Year Check

//检查闰年
public void isLeapYear(){
    LocalDate today = LocalDate.now();
    if(today.isLeapYear()){
        System.out.println("This year is Leap year");
    } else {
        System.out.println("2018 is not a Leap year");
    }
}

15. Calculate Period Between Dates

//计算两个日期之间的天数和月数
public void calcDateDays(){
    LocalDate today = LocalDate.now();
    LocalDate java8Release = LocalDate.of(2018, Month.MAY, 14);
    Period periodToNextJavaRelease = Period.between(today, java8Release);
    System.out.println("Months left between today and Java 8 release : " + periodToNextJavaRelease.getMonths());
}

16. Date‑Time with Zone Offset

// 包含时差信息的日期和时间
public void ZoneOffset(){
    LocalDateTime datetime = LocalDateTime.of(2018, Month.FEBRUARY, 14, 19, 30);
    ZoneOffset offset = ZoneOffset.of("+05:30");
    OffsetDateTime date = OffsetDateTime.of(datetime, offset);
    System.out.println("Date and Time with timezone offset in Java : " + date);
}

17. Get Current Timestamp

//获取当前的时间戳
public void getTimestamp(){
    Instant timestamp = Instant.now();
    System.out.println("What is value of this instant " + timestamp);
}

18. Format and Parse Dates with Predefined Formatters

// 使用预定义的格式化工具去解析或格式化日期
public void formateDate(){
    String dayAfterTommorrow = "20180210";
    LocalDate formatted = LocalDate.parse(dayAfterTommorrow, DateTimeFormatter.BASIC_ISO_DATE);
    System.out.printf("Date generated from String %s is %s %n", dayAfterTommorrow, formatted);
}

Full Source Code

package com.wq.study.java8.date;

import java.time.Clock;
import java.time.Instant;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.Month;
import java.time.MonthDay;
import java.time.OffsetDateTime;
import java.time.ZoneOffset;
import java.time.Period;
import java.time.YearMonth;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;
import java.util.Date;

public class DateTest {
    //获取今天的日期
    public void getCurrentDate(){
        LocalDate today = LocalDate.now();
        System.out.println("Today's Local date : " + today);
        Date date = new Date();
        System.out.println(date);
    }
    //获取年、月、日信息
    public void getDetailDate(){
        LocalDate today = LocalDate.now();
        int year = today.getYear();
        int month = today.getMonthValue();
        int day = today.getDayOfMonth();
        System.out.printf("Year : %d  Month : %d  day : %d t %n", year, month, day);
    }
    //处理特定日期
    public void handleSpecilDate(){
        LocalDate dateOfBirth = LocalDate.of(2018, 01, 21);
        System.out.println("The specil date is : " + dateOfBirth);
    }
    //判断两个日期是否相等
    public void compareDate(){
        LocalDate today = LocalDate.now();
        LocalDate date1 = LocalDate.of(2018, 01, 21);
        if(date1.equals(today)){
            System.out.printf("TODAY %s and DATE1 %s are same date %n", today, date1);
        }
    }
    //处理周期性的日期
    public void cycleDate(){
        LocalDate today = LocalDate.now();
        LocalDate dateOfBirth = LocalDate.of(2018, 01, 21);
        MonthDay birthday = MonthDay.of(dateOfBirth.getMonth(), dateOfBirth.getDayOfMonth());
        MonthDay currentMonthDay = MonthDay.from(today);
        if(currentMonthDay.equals(birthday)){
            System.out.println("Many Many happy returns of the day !!");
        } else {
            System.out.println("Sorry, today is not your birthday");
        }
    }
    //获取当前时间
    public void getCurrentTime(){
        LocalTime time = LocalTime.now();
        System.out.println("local time now : " + time);
    }
    //增加小时
    public void plusHours(){
        LocalTime time = LocalTime.now();
        LocalTime newTime = time.plusHours(2); // 增加两小时
        System.out.println("Time after 2 hours : " +  newTime);
    }
    //如何计算一周后的日期
    public void nextWeek(){
        LocalDate today = LocalDate.now();
        LocalDate nextWeek = today.plus(1, ChronoUnit.WEEKS);
        System.out.println("Today is : " + today);
        System.out.println("Date after 1 week : " + nextWeek);
    }
    //计算一年前或一年后的日期
    public void minusDate(){
        LocalDate today = LocalDate.now();
        LocalDate previousYear = today.minus(1, ChronoUnit.YEARS);
        System.out.println("Date before 1 year : " + previousYear);
        LocalDate nextYear = today.plus(1, ChronoUnit.YEARS);
        System.out.println("Date after 1 year : " + nextYear);
    }
    public void clock(){
        // 根据系统时间返回当前时间并设置为UTC。
        Clock clock = Clock.systemUTC();
        System.out.println("Clock : " + clock);
        // 根据系统时钟区域返回时间
        Clock defaultClock = Clock.systemDefaultZone();
        System.out.println("Clock : " + clock);
    }
    //如何用Java判断日期是早于还是晚于另一个日期
    public void isBeforeOrIsAfter(){
        LocalDate today = LocalDate.now(); 
        LocalDate tomorrow = LocalDate.of(2018, 1, 29);
        if(tomorrow.isAfter(today)){
            System.out.println("Tomorrow comes after today");
        }
        LocalDate yesterday = today.minus(1, ChronoUnit.DAYS);
        if(yesterday.isBefore(today)){
            System.out.println("Yesterday is day before today");
        }
    }
    //时区处理
    public void getZoneTime(){
        //设置时区
        ZoneId america = ZoneId.of("America/New_York");
        LocalDateTime localtDateAndTime = LocalDateTime.now();
        ZonedDateTime dateAndTimeInNewYork  = ZonedDateTime.of(localtDateAndTime, america );
        System.out.println("现在的日期和时间在特定的时区 : " + dateAndTimeInNewYork);
    }
    //使用 YearMonth类处理特定的日期
    public void checkCardExpiry(){
        YearMonth currentYearMonth = YearMonth.now();
        System.out.printf("Days in month year %s: %d%n", currentYearMonth, currentYearMonth.lengthOfMonth());
        YearMonth creditCardExpiry = YearMonth.of(2028, Month.FEBRUARY);
        System.out.printf("Your credit card expires on %s %n", creditCardExpiry);
    }
    //检查闰年
    public void isLeapYear(){
        LocalDate today = LocalDate.now();
        if(today.isLeapYear()){
            System.out.println("This year is Leap year");
        } else {
            System.out.println("2018 is not a Leap year");
        }
    }
    //计算两个日期之间的天数和月数
    public void calcDateDays(){
        LocalDate today = LocalDate.now();
        LocalDate java8Release = LocalDate.of(2018, Month.MAY, 14);
        Period periodToNextJavaRelease = Period.between(today, java8Release);
        System.out.println("Months left between today and Java 8 release : " + periodToNextJavaRelease.getMonths() );
    }
    // 包含时差信息的日期和时间
    public void ZoneOffset(){
        LocalDateTime datetime = LocalDateTime.of(2018, Month.FEBRUARY, 14, 19, 30);
        ZoneOffset offset = ZoneOffset.of("+05:30");
        OffsetDateTime date = OffsetDateTime.of(datetime, offset);  
        System.out.println("Date and Time with timezone offset in Java : " + date);
    }
    // 获取时间戳
    public void getTimestamp(){
        Instant timestamp = Instant.now();
        System.out.println("What is value of this instant " + timestamp);
    }
    // 使用预定义的格式化工具去解析或格式化日期
    public void formateDate(){
        String dayAfterTommorrow = "20180210";
        LocalDate formatted = LocalDate.parse(dayAfterTommorrow, DateTimeFormatter.BASIC_ISO_DATE);
        System.out.printf("Date generated from String %s is %s %n", dayAfterTommorrow, formatted);
    }
    public static void main(String[] args) {
        DateTest dt = new DateTest();
        dt.formateDate();
    }
}

Summary of Java 8 Date‑Time API

The new API provides thread‑safe, immutable classes such as LocalDate , LocalTime , and ZonedDateTime , replaces the old java.util.Date and SimpleDateFormat , and includes comprehensive support for time zones, offsets, periods, and predefined formatters.