Java ZonedDateTime.format issue

Question

Running into ZonedDateTime formatting issue. It formats end of December, 2020 dates as 2021 dates. Java snippet

ZonedDateTime z1 = ZonedDateTime.of(LocalDateTime.of(2020, 12, 31, 0, 0), ZoneId.of("America/New_York"));
z1.format(DateTimeFormatter.ofPattern("YYYY-MM-dd"))
// yields "2021-12-31"

Same goes for December 28th, 29th, 30th. Same result for different time-zones. Repeats for December 30 2019 (formats as 2020-12-30).

Original Clojure snippet

(let [zdt (ZonedDateTime/of (LocalDateTime/of 2020 12 31 0 0) (ZoneId/of "America/New_York"))
      f (DateTimeFormatter/ofPattern "YYYY-MM-dd")]
  (.format zdt f))
; => "2021-12-31"

I am able to reproduce on:

MacOS HotSpot Java 10 (java version "10.0.2" 2018-07-17)
OpenJDK version "11.0.9.1" 2020-11-04

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score 5 · Accepted Answer · answered Jan 01 '21 at 08:15

5

Change the pattern string to yyyy-MM-dd. Refer to the javadoc for class DateTimeFormatter to understand the difference between YYYY and yyyy.

ZonedDateTime z1 = ZonedDateTime.of(LocalDateTime.of(2020, 12, 31, 0, 0), ZoneId.of("America/New_York"));
System.out.println(z1.format(DateTimeFormatter.ofPattern("yyyy-MM-dd")));

Result:

2020-12-31

answered Jan 01 '21 at 08:15

Abra

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yes, that works – Light-wharf Jan 01 '21 at 08:26

score 2 · Answer 2 · answered Jan 01 '21 at 08:24

2

Ok, found it. It’s just my formatting mistake.

Y is for week-based-year
y is for era year
u is for just year

So use "uuuu-MM-dd" and it all works

answered Jan 01 '21 at 08:24

Light-wharf

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Or, much more simply, `DateTimeFormatter.ISO_LOCAL_DATE`. – chrylis -cautiouslyoptimistic- Jan 01 '21 at 08:55

Java ZonedDateTime.format issue

2 Answers2

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