java - Calendar.getInstance().getTime() returning date in "GMT" instead of Default TimeZone - 


calendar c = calendar.getinstance(); system.out.println(c.gettime()); c.set(2007, 0, 1); system.out.println(c.gettime());

output:

tue sep 12 12:36:24 ist 2017

mon jan 01 12:36:24 ist 2007

but, when use same code in different environment, output changes below:

output:

tue sep 12 12:36:24 ist 2017

mon jan 01 12:36:24 gmt 2007

fyi, tried print timezone of calendar instance, before , after setting values , both in "ist".

i want know root cause of this.

the second output in question correct , expected behaviour on jvm running irish time (europe/dublin). on september 12, 2017 ireland on summer time (dst). while not documented, date.tostring() (which invoke implicitly when printing date c.gettime()) prints date , time in jvm’s time zone, in september rendered ist irish summer time.

when set date on calendar object using irish time, hour of day preserved; in case jan 01 2007 12:36:24 irish standard time. imagine confusion if both irish summer time , irish standard time rendered ist. not able distinguish. instead, since irish standard time coincides gmt, date.tostring() prints when date not in summer time part of year (which january isn’t).

my guess first output jvm running india time. rendered ist, , since india doesn’t use summer time, same abbreviation given summer , winter.

java.time

before understanding explanation behaviour observed, posted comment outdated , modern java date , time classes. still don’t think comment way off, though. modern equivalent of code:

    zoneddatetime zdt = zoneddatetime.now(zoneid.of("europe/dublin"));     system.out.println(zdt);     zdt = zdt.with(localdate.of(2007, month.january, 1));     system.out.println(zdt);

it prints

2017-09-12t11:45:33.921+01:00[europe/dublin] 2007-01-01t11:45:33.921z[europe/dublin]

if want use jvm’s time zone setting, use zoneid.systemdefault() instead of zoneid.of("europe/dublin"). name states, contrary date, zoneddatetime include time zone. corresponds more old calendar class. can see, tostring method prints offset utc (z meaning 0 offset) , time zone name in unambiguous region/city format. believe leaves lot less room confusion. if want print date in specific format, use datetimeformatter.

appendix: sample output code

for sake of completeness, here outputs code when running different time zones may rendered ist:

  • europe/dublin (agrees second output)

    tue sep 12 11:19:28 ist 2017 mon jan 01 11:19:28 gmt 2007

  • asia/tel_aviv

    tue sep 12 13:19:28 idt 2017 mon jan 01 13:19:28 ist 2007

  • asia/kolkata (agrees first output)

    tue sep 12 15:49:28 ist 2017 mon jan 01 15:49:28 ist 2007

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