Introduction

• Before Java 8, date and time handling was done using classes (Date, Calendar etc) from the java.util package.
• However, the old Date-Time API had several disadvantages:
  • Mutability: Date and Calendar classes are mutable, making them not thread-safe.
  • Poor API Design: Month index starts from 0 (January), which is confusing for developers.
  • Limited Functionality: Lacks built-in support for time zones and formatting/parsing operations were cumbersome.
  • Complexity: Calendar and GregorianCalendar are verbose and difficult to use for simple tasks.
• To overcome these problems, Java 8 introduced the New Date and Time API in the java.time package, which is immutable, thread-safe and much easier to use.

New Date API:

• Java 8 introduced a new Date API with the java.time.LocalDate class to represent dates in a simple, clean and immutable way.
• It handles year, month and day without time and timezone, making it ideal for working with pure dates like birthdays, holidays, and schedules.
• Some important date-related classes present in new API are as follows:

  S.No	Class / Interface	Important Methods	Purpose / Description
  1	LocalDate	now(), of(), plusDays(), minusDays(), getDayOfWeek(), isLeapYear()	Represents a date (year, month, day) without time and timezone.
  2	LocalDateTime	now(), of(), plusHours(), minusMinutes(), toLocalDate(), toLocalTime()	Represents a date + time (year, month, day, hour, minute, second) without timezone.
  3	ZonedDateTime	now(), of(), withZoneSameInstant(), getZone(), toLocalDateTime()	Represents a date + time with a specific timezone.
  4	OffsetDateTime	now(), of(), getOffset(), withOffsetSameInstant(), toLocalDateTime()	Represents date and time with an offset from UTC but not full time zone rules.
  5	Year	now(), of(), isLeap(), plusYears(), minusYears()	Represents a specific year.
  6	YearMonth	now(), of(), lengthOfMonth(), isLeapYear(), plusMonths()	Represents a year and month without a day.
  7	MonthDay	now(), of(), isValidYear(), atYear()	Represents a combination of month and day, without year.

• Program 1:

  import java.time.*;
  
  public class MainApp1
  {
      public static void main(String[] args)
      {
          // 1. LocalDate
          LocalDate today = LocalDate.now();
          LocalDate specificDate = LocalDate.of(2025, 9, 19);
          LocalDate nextWeek = today.plusDays(7);
          LocalDate lastWeek = today.minusDays(7);
          DayOfWeek dayOfWeek = today.getDayOfWeek();
          boolean isLeap = today.isLeapYear();
  
          System.out.println("------ LocalDate ------");
          System.out.println("Today: " + today);
          System.out.println("Specific Date: " + specificDate);
          System.out.println("Next Week: " + nextWeek);
          System.out.println("Last Week: " + lastWeek);
          System.out.println("Day of Week: " + dayOfWeek);
          System.out.println("Is Leap Year: " + isLeap);
          System.out.println();
  
          // 2. LocalDateTime
          LocalDateTime currentDateTime = LocalDateTime.now();
          LocalDateTime specificDateTime = LocalDateTime.of(2025, 9, 19, 10, 30, 45);
          LocalDateTime plusHours = currentDateTime.plusHours(5);
          LocalDateTime minusMinutes = currentDateTime.minusMinutes(15);
  
          System.out.println("------ LocalDateTime ------");
          System.out.println("Current DateTime: " + currentDateTime);
          System.out.println("Specific DateTime: " + specificDateTime);
          System.out.println("Plus 5 Hours: " + plusHours);
          System.out.println("Minus 15 Minutes: " + minusMinutes);
          System.out.println("To LocalDate: " + currentDateTime.toLocalDate());
          System.out.println("To LocalTime: " + currentDateTime.toLocalTime());
          System.out.println();
  
          // 3. ZonedDateTime
          ZonedDateTime zonedNow = ZonedDateTime.now();
          ZonedDateTime specificZoned = ZonedDateTime.of(2025, 9, 19, 10, 30, 0, 0, ZoneId.of("Asia/Kolkata"));
          ZonedDateTime convertedZone = zonedNow.withZoneSameInstant(ZoneId.of("Europe/London"));
  
          System.out.println("------ ZonedDateTime ------");
          System.out.println("Current ZonedDateTime: " + zonedNow);
          System.out.println("Specific ZonedDateTime: " + specificZoned);
          System.out.println("Converted to London Zone: " + convertedZone);
          System.out.println("Zone: " + zonedNow.getZone());
          System.out.println("To LocalDateTime: " + zonedNow.toLocalDateTime());
          System.out.println();
  
          // 4. OffsetDateTime
          OffsetDateTime offsetNow = OffsetDateTime.now();
          OffsetDateTime specificOffset = OffsetDateTime.of(2025, 9, 19, 10, 30, 0, 0, ZoneOffset.ofHours(5));
          OffsetDateTime newOffset = offsetNow.withOffsetSameInstant(ZoneOffset.ofHours(2));
  
          System.out.println("------ OffsetDateTime ------");
          System.out.println("Current OffsetDateTime: " + offsetNow);
          System.out.println("Specific OffsetDateTime: " + specificOffset);
          System.out.println("Offset: " + offsetNow.getOffset());
          System.out.println("Converted Offset: " + newOffset);
          System.out.println("To LocalDateTime: " + offsetNow.toLocalDateTime());
          System.out.println();
      }
  }

  Output:

  ------ LocalDate ------
  Today: 2025-09-19
  Specific Date: 2025-09-19
  Next Week: 2025-09-26
  Last Week: 2025-09-12
  Day of Week: FRIDAY
  Is Leap Year: false
  
  ------ LocalDateTime ------
  Current DateTime: 2025-09-19T08:57:58.855210900
  Specific DateTime: 2025-09-19T10:30:45
  Plus 5 Hours: 2025-09-19T13:57:58.855210900
  Minus 15 Minutes: 2025-09-19T08:42:58.855210900
  To LocalDate: 2025-09-19
  To LocalTime: 08:57:58.855210900
  
  ------ ZonedDateTime ------
  Current ZonedDateTime: 2025-09-19T08:57:58.856207900+05:30[Asia/Calcutta]
  Specific ZonedDateTime: 2025-09-19T10:30+05:30[Asia/Kolkata]
  Converted to London Zone: 2025-09-19T04:27:58.856207900+01:00[Europe/London]
  Zone: Asia/Calcutta
  To LocalDateTime: 2025-09-19T08:57:58.856207900
  
  ------ OffsetDateTime ------
  Current OffsetDateTime: 2025-09-19T08:57:58.860198200+05:30
  Specific OffsetDateTime: 2025-09-19T10:30+05:00
  Offset: +05:30
  Converted Offset: 2025-09-19T05:27:58.860198200+02:00
  To LocalDateTime: 2025-09-19T08:57:58.860198200

• Program 2:

  import java.time.*;
  
  public class MainApp2
  {
      public static void main(String[] args)
      {
          // 5. Year
          Year thisYear = Year.now();
          Year specificYear = Year.of(2028);
          boolean leap = specificYear.isLeap();
          Year nextYear = thisYear.plusYears(1);
          Year lastYear = thisYear.minusYears(1);
  
          System.out.println("------ Year ------");
          System.out.println("This Year: " + thisYear);
          System.out.println("Specific Year: " + specificYear);
          System.out.println("Is Leap Year: " + leap);
          System.out.println("Next Year: " + nextYear);
          System.out.println("Last Year: " + lastYear);
          System.out.println();
  
          // 6. YearMonth
          YearMonth currentMonth = YearMonth.now();
          YearMonth specificMonth = YearMonth.of(2025, 12);
          int lengthOfMonth = specificMonth.lengthOfMonth();
          boolean isLeapMonthYear = specificMonth.isLeapYear();
          YearMonth nextMonth = currentMonth.plusMonths(1);
  
          System.out.println("------ YearMonth ------");
          System.out.println("Current YearMonth: " + currentMonth);
          System.out.println("Specific YearMonth: " + specificMonth);
          System.out.println("Length of Month: " + lengthOfMonth);
          System.out.println("Is Leap Year: " + isLeapMonthYear);
          System.out.println("Next Month: " + nextMonth);
          System.out.println();
  
          // 7. MonthDay
          MonthDay todayMonthDay = MonthDay.now();
          MonthDay specificMonthDay = MonthDay.of(12, 25);
          boolean validForYear = specificMonthDay.isValidYear(2025);
          LocalDate dateFromMonthDay = specificMonthDay.atYear(2025);
  
          System.out.println("------ MonthDay ------");
          System.out.println("Today MonthDay: " + todayMonthDay);
          System.out.println("Specific MonthDay: " + specificMonthDay);
          System.out.println("Is Valid for 2025: " + validForYear);
          System.out.println("Converted to LocalDate: " + dateFromMonthDay);
      }
  }

  Output:

  ------ Year ------
  This Year: 2025
  Specific Year: 2028
  Is Leap Year: true
  Next Year: 2026
  Last Year: 2024
  
  ------ YearMonth ------
  Current YearMonth: 2025-09
  Specific YearMonth: 2025-12
  Length of Month: 31
  Is Leap Year: false
  Next Month: 2025-10
  
  ------ MonthDay ------
  Today MonthDay: --09-19
  Specific MonthDay: --12-25
  Is Valid for 2025: true
  Converted to LocalDate: 2025-12-25

New Time API:

• Java 8 introduced a new Time API with the java.time.LocalTime class to represent time in a simple, clean, and immutable way.
• It handles hour, minute, second and nanosecond without date and timezone, making it ideal for working with pure times like meeting times, alarms, and schedules.
• Some important time-related classes present in new API are as follows:

  S.No	Class / Interface	Important Methods	Purpose / Description
  1	LocalTime	now(), of(), plusHours(), minusMinutes(), getHour(), getMinute()	Represents a time (hour, minute, second, nanosecond) without date and timezone.
  2	OffsetTime	now(), of(), getOffset(), withOffsetSameInstant(), toLocalTime()	Represents time with an offset from UTC, but not full time zone rules.
  3	Duration	between(), ofHours(), ofMinutes(), toHours(), toMinutes()	Represents a time-based amount of time, such as seconds, minutes, or hours.
  4	Instant	now(), ofEpochSecond(), plusSeconds(), minusMillis()	Represents a moment on the timeline in UTC, useful for timestamps.
  5	ChronoUnit	between(), plus(), minus()	Used to measure amounts of time in units like hours, minutes, seconds, etc.

• Program 1:

  import java.time.*;
  import java.time.temporal.ChronoUnit;
  
  public class MainApp3
  {
      public static void main(String[] args)
      {
          // 1. LocalTime
          LocalTime nowTime = LocalTime.now();
          LocalTime specificTime = LocalTime.of(14, 30, 45);
          LocalTime plusHours = nowTime.plusHours(2);
          LocalTime minusMinutes = nowTime.minusMinutes(15);
  
          System.out.println("------ LocalTime ------");
          System.out.println("Current Time: " + nowTime);
          System.out.println("Specific Time: " + specificTime);
          System.out.println("Plus 2 Hours: " + plusHours);
          System.out.println("Minus 15 Minutes: " + minusMinutes);
          System.out.println("Hour: " + nowTime.getHour());
          System.out.println("Minute: " + nowTime.getMinute());
          System.out.println();
  
          // 2. OffsetTime
          OffsetTime offsetNow = OffsetTime.now();
          OffsetTime specificOffset = OffsetTime.of(14, 30, 0, 0, ZoneOffset.ofHours(5));
          OffsetTime newOffset = offsetNow.withOffsetSameInstant(ZoneOffset.ofHours(2));
  
          System.out.println("------ OffsetTime ------");
          System.out.println("Current OffsetTime: " + offsetNow);
          System.out.println("Specific OffsetTime: " + specificOffset);
          System.out.println("Converted Offset: " + newOffset);
          System.out.println("Offset: " + offsetNow.getOffset());
          System.out.println("To LocalTime: " + offsetNow.toLocalTime());
          System.out.println();
  
          // 3. Duration
          LocalTime start = LocalTime.of(9, 0);
          LocalTime end = LocalTime.of(17, 30);
          Duration duration = Duration.between(start, end);
          Duration plusDuration = duration.plusHours(1);
  
          System.out.println("------ Duration ------");
          System.out.println("Duration between 9:00 and 17:30: " + duration.toHours() + " hours");
          System.out.println("Duration plus 1 hour: " + plusDuration.toHours() + " hours");
          System.out.println();
  
          // 4. Instant
          Instant instantNow = Instant.now();
          Instant instantLater = instantNow.plusSeconds(3600);
  
          System.out.println("------ Instant ------");
          System.out.println("Current Instant: " + instantNow);
          System.out.println("Instant after 1 hour: " + instantLater);
          System.out.println();
  
          // 5. ChronoUnit
          long minutesBetween = ChronoUnit.MINUTES.between(start, end);
          long hoursBetween = ChronoUnit.HOURS.between(start, end);
  
          System.out.println("------ ChronoUnit ------");
          System.out.println("Minutes between 9:00 and 17:30: " + minutesBetween);
          System.out.println("Hours between 9:00 and 17:30: " + hoursBetween);
      }
  }

  Output:

  ------ LocalTime ------
  Current Time: 08:57:58.123
  Specific Time: 14:30:45
  Plus 2 Hours: 10:57:58.123
  Minus 15 Minutes: 08:42:58.123
  Hour: 8
  Minute: 57
  
  ------ OffsetTime ------
  Current OffsetTime: 08:57:58.123+05:30
  Specific OffsetTime: 14:30+05:00
  Converted Offset: 05:27:58.123+02:00
  Offset: +05:30
  To LocalTime: 08:57:58.123
  
  ------ Duration ------
  Duration between 9:00 and 17:30: 8 hours
  Duration plus 1 hour: 9 hours
  
  ------ Instant ------
  Current Instant: 2025-09-19T03:27:58.123Z
  Instant after 1 hour: 2025-09-19T04:27:58.123Z
  
  ------ ChronoUnit ------
  Minutes between 9:00 and 17:30: 510
  Hours between 9:00 and 17:30: 8