java의 time 관련 표현 방법 정리
java.time package : https://docs.oracle.com/javase/8/docs/api/java/time/package-summary.html
비교 대상
LocalDateTime, OffsetDateTime, ZonedDateTime
LocalDateTime
ISO-8601 캘린더 시스템의 타임존 개념이 없는, 날짜-시간 시스템.
ex : 2023-08-19T09:33:26.590
해당 컴퓨터의 타임존에 맞춘 시간을 의미
서울에서 new LocalDateTime()을 하면 서울의 현재 시각이 나온다
ISO-8601는 날짜와 시간과 관련된 국제표준이다.
ISO-8601의 핵심은 - : T W Z 같은 정해진 문자만 써서 작성한다는 것
ZonedDateTime
ISO-8601 캘린더에 정의된 타임존을 포함한 날짜-시간 시스템
ex : 2023-08-19T09:33:26.591+09:00[Asia/Seoul]
ex 타임존 : +09:00[Asia/Seoul]
OffsetDateTime
date-time + offset (UTC/그리니치에서부터의 오프셋만을 표현)
offset : 타임존의 정보에서 존에 대한 정보를 제거한 내역 ( +09:00[Asia/Seoul] 에서 +09:00가 offset )
ex : 2023-08-19T09:33:26.591+09:00
ex offset : +09:00
정보의 양
LocalDateTime < OffsetDateTime < ZonedDateTime
example code
LocalDateTime localDateTime = LocalDateTime.now();
OffsetDateTime offsetDateTime = OffsetDateTime.now();
ZonedDateTime zonedDateTime = ZonedDateTime.now();
System.out.println(localDateTime);
System.out.println(offsetDateTime);
System.out.println(zonedDateTime);
System.out.println(localDateTime.atOffset(ZoneOffset.ofHours(4)));
System.out.println(localDateTime.atZone(ZoneId.of("Africa/Cairo")));
output
2023-08-19T09:57:22.117
2023-08-19T09:57:22.118+09:00
2023-08-19T09:57:22.118+09:00[Asia/Seoul]
2023-08-19T09:57:22.117+04:00
2023-08-19T09:57:22.117+02:00[Africa/Cairo] |
DateTimeFormatter
https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html
ISO_LOCAL_DATE_TIME - yyyy-MM-dd'T'HH:mm:ss
DateTimeFormatter를 이용해 formatter을 맞추고 싶은 경우
yyyy-MM-dd'T'HH:mm:ss -> 2023-08-19T09:57:22.117
yyyy-MM-dd'T'HH:mm:ss.SSSZZ -> 2023-08-19T09:57:22.118+09:00
ms뒤에 Zone의 표현 알파벳, 개수에 따라 offset의 표현되는 방식이 다르다
Z :
One, two or three letters outputs the hour and minute, without a colon, such as '+0130'. The output will be '+0000' when the offset is zero.
2023-08-19T10:48:14.489+0900
Four letters outputs the full form of localized offset, equivalent to four letters of Offset-O.
The output will be the corresponding localized offset text if the offset is zero.
2023-08-19T10:48:14.489GMT+09:00
Five letters outputs the hour, minute, with optional second if non-zero, with colon.
It outputs 'Z' if the offset is zero
2023-08-19T10:48:14.489+09:00
FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSZ");
System.out.println(FORMATTER.format(zonedDateTime));
FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSZZZZ");
System.out.println(FORMATTER.format(zonedDateTime));
FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSZZZZZ");
System.out.println(FORMATTER.format(zonedDateTime));
2023-08-19T10:48:14.489+0900
2023-08-19T10:48:14.489GMT+09:00
2023-08-19T10:48:14.489+09:00 |
X:
One letter outputs just the hour, such as '+01',
unless the minute is non-zero in which case the minute is also output, such as '+0130'.
2023-08-19T10:48:14.489+09
Two letters outputs the hour and minute, without a colon, such as '+0130'.
2023-08-19T10:48:14.489+0900
Three letters outputs the hour and minute, with a colon, such as '+01:30'.
2023-08-19T10:48:14.489+09:00
Four letters outputs the hour and minute and optional second, without a colon, such as '+013015'.
Five letters outputs the hour and minute and optional second, with a colon, such as '+01:30:15'.
FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSx");
System.out.println(FORMATTER.format(zonedDateTime));
FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSxx");
System.out.println(FORMATTER.format(zonedDateTime));
FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSxxx");
System.out.println(FORMATTER.format(zonedDateTime));
FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSxxxx");
System.out.println(FORMATTER.format(zonedDateTime));
FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSxxxxx");
System.out.println(FORMATTER.format(zonedDateTime));
2023-08-19T10:48:14.489+09
2023-08-19T10:48:14.489+0900
2023-08-19T10:48:14.489+09:00
2023-08-19T10:48:14.489+0900
2023-08-19T10:48:14.489+09:00 |