java.time.LocalDateTime (also ZonedDateTime). Fails to return one year backward when minus 1 month with formatting

Question

I'm doing this

import java.time.LocalDateTime
import java.time.temporal.ChronoUnit


LocalDateTime doy = LocalDateTime.now();
LocalDateTime d = LocalDateTime.of(doy.getYear(), doy.getMonth(), doy.getDayOfMonth(),0,0,0,0);
d.plus(-1,ChronoUnit.MONTHS);
return d.atZone(ZoneOffset.systemDefault()).withZoneSameInstant(ZoneOffset.UTC).format(DateTimeFormatter.ofPattern("YYYY-MM-dd'T'HH:mm:ss.SSSX"))

d contains 2016-12-28T08:00:00.000Z I want to get 2015-12-28T00:00:00.000Z

I'm on mac OSX java SE 8 1.8.0_45 also tried java SE 8 1.8.0_72

What am I doing wrong ?

Adding more explanation here

Apparently part of my problem is related to formatting

ZonedDateTime doy = ZonedDateTime.now(ZoneOffset.UTC);
ZonedDateTime d = ZonedDateTime.of(LocalDateTime.of(doy.getYear(), doy.getMonth(), doy.getDayOfMonth(),0,0,0,0),ZoneOffset.UTC);
System.out.println(d);
System.out.println(d.plus(-1,ChronoUnit.MONTHS));
System.out.println(d.minusMonths(1));
System.out.println(d.plus(-1,ChronoUnit.MONTHS).format(DateTimeFormatter.ofPattern("YYYY-MM-dd'T'HH:mm:ss.SSSX")));

output

2016-01-28T00:00Z
2015-12-28T00:00Z
2015-12-28T00:00Z
2016-12-28T00:00:00.000Z

The last one should be 2015-12-28T00:00:00.000Z

System.out.println(d.minusMonths(1).format(DateTimeFormatter.ofPattern("YYYY-MM-dd'T'HH:mm:ss.SSSX")));

Gives the same result

Answer 1

You can do something like this:

LocalDateTime doy = LocalDateTime.now();
LocalDateTime d = doy.minusYears(1);

and then

LocalDateTime d2 = d.minusMonth(1);
return d2;

from API java 8 ( LINK ):

minusYears(long years)

Returns a copy of this LocalDateTime with the specified number of years subtracted.

and d.minusMonth

Returns a copy of this LocalDateTime with the specified number of months subtracted.

Answer 2

YYYY is year value for "year-week" style dates, as in 2006W52. It may be off the year-of-era value by +1 or -1 if the week in question straddles year boundary. Looks like you have chosen the last week of the year.

See http://en.wikipedia.org/wiki/ISO_8601#Week_dates

See also: java.time.LocalDateTime (also ZonedDateTime). Fails to return one year backward when minus 1 month with formatting

Answer 3

I found a solution to my problem

ZonedDateTime doy = ZonedDateTime.now(ZoneOffset.UTC);
ZonedDateTime d = ZonedDateTime.of(LocalDateTime.of(doy.getYear(), doy.getMonth(), doy.getDayOfMonth(),0,0,0,0),ZoneOffset.UTC);

DateTimeFormatterBuilder builder = new DateTimeFormatterBuilder();
builder.appendValue(ChronoField.YEAR).append(DateTimeFormatter.ofPattern("-MM-dd'T'HH:mm:ss.SSSX"));
DateTimeFormatter formatter = builder.toFormatter();

System.out.println(d.plus(-1,ChronoUnit.MONTHS).format(formatter));

output

2015-12-28T00:00:00.000Z

So I guess Something is wrong with the pattern DateTimeFormatter.ofPattern("YYYY-MM-dd'T'HH:mm:ss.SSSX")

Actually this formatting DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSX") works

Damn it !!!!

Anyone can explain why my tests were passing yesterday and not anymore today, what's so special about January 28th ??????

Answer 4

Since you want to backward one month , then you should do this for example:

LocalDateTime d = LocalDateTime.of(2016, Month.JANUARY, 28, 0, 0, 0);
System.out.println(d);
System.out.println(d.minusMonths(1));

Answer 5

I think you are looking for d.minusMonths(...). I've never used the "plus" method.