It is recommended to use the java.time package to handle dates and times in Java 8 and above. 1. LocalDate and LocalTime are used for dates and times without time zones, such as 2025-04-05 and 14:30:45 respectively; 2. Use now() to get the current date or time, and of() to create a specified date or time; 3. Common operations include adding and subtracting days, months, etc., and the object is immutable, and each operation returns a new instance; 4. LocalDateTime combines date and time but no time zone, ZonedDateTime supports time zone; 5. Use ZoneId to define the time zone and convert it through atZone(), and use withZoneSameInstant() to implement time zone conversion; 6. Duration calculates the time difference, Period calculates the date difference, and ChronoUnit can obtain the exact difference value; 7. DateTimeFormatter For formatting and parsing, please note that the pattern string must be consistent with the input. Familiar with these core categories and conversion methods can deal with most business scenarios.

To handle dates and times in Java 8 and above, it is recommended to use the java.time package. This package is part of JSR-310, replacing the old Date and Calendar classes, providing a clearer and easier-to-use API.

LocalDate and LocalTime: The basis for processing dates and times

LocalDate represents a date without a time zone, such as 2025-04-05; LocalTime represents a time without a time zone, such as 14:30:45. These two classes are suitable for scenarios where time zones are not required to be considered.

• Get the current date or time:

   LocalDate today = LocalDate.now();
  LocalTime now = LocalTime.now();

• Create a specified date or time:

  

   LocalDate date = LocalDate.of(2025, 4, 5);
  LocalTime time = LocalTime.of(14, 30, 45);

• Common operations: Add or subtract days, months, etc.

   LocalDate tomorrow = today.plusDays(1);
  LocalDate nextMonth = today.plusMonths(1);

Note: These objects are immutable and a new instance is returned for each operation.

LocalDateTime and ZonedDateTime: Combining date and time, supporting time zones

LocalDateTime is a combination of LocalDate and LocalTime , but still does not contain time zone information. If you need to consider the time zone, use ZonedDateTime .

• Create LocalDateTime :

   LocalDateTime dateTime = LocalDateTime.of(2025, 4, 5, 14, 30);

• Convert LocalDateTime to time with time zone:

   ZoneId zone = ZoneId.of("Asia/Shanghai");
  ZonedDateTime zoned = dateTime.atZone(zone);

• Get the current time with time zone:

   ZonedDateTime nowInTokyo = ZonedDateTime.now(ZoneId.of("Asia/Tokyo"));

Time zone conversion is a common requirement, such as converting UTC time to local time:

 ZonedDateTime utcTime = ZonedDateTime.now(ZoneOffset.UTC);
ZonedDateTime localTime = utcTime.withZoneSameInstant(zone);

Duration and Period: Calculate the time difference

To calculate the interval between two time points, you can use Duration (for time) and Period (for date).

• Calculate date differences using Period :

   LocalDate start = LocalDate.of(2025, 4, 1);
  LocalDate end = LocalDate.of(2025, 5, 10);
  Period period = Period.between(start, end); // Get 1 month and 9 days

• Use Duration to calculate the time difference:

   LocalTime start = LocalTime.of(10, 0);
  LocalTime end = LocalTime.of(12, 30);
  Duration duration = Duration.between(start, end); // Get 9000 seconds

If you have two ZonedDateTime , you can also use Duration or ChronoUnit to get the exact difference:

 long hoursBetween = ChronoUnit.HOURS.between(zonedStart, zonedEnd);

Format and parsing: Convert strings and time to each other

Formatting output and parsing input are common operations in daily development. java.time provides DateTimeFormatter to complete this task.

• Format date time:

   DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
  String text = LocalDateTime.now().format(formatter);

• Parsing the string as datetime:

   String input = "2025-04-05 14:30:45";
  LocalDateTime parsed = LocalDateTime.parse(input, formatter);

Note: The pattern string must be strictly consistent with the input format, otherwise an exception will be thrown. It is recommended to handle exceptions when parsing user input.

Basically that's it. java.time is designed to be more intuitive. As long as you are familiar with several core classes and the conversion method between them, you can deal with most business scenarios.

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