I thought 2011-10-23 12:00:00 would remain the same as UTC and that the Converted date would be 2011-10-23 17:00:00.
DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date dt = formatter.parse("2011-10-23 12:00:00");
LocalDateTime ldt = new DateTime(dt).withZone(DateTimeZone.UTC).toLocalDateTime();
LOGGER.warn("Original date: " + ldt.toDateTime().toDate().toString());
DateTime cvtldt = ldt.toDateTime(DateTimeZone.forID("-05:00"));
LOGGER.warn("Converted date: " + cvtldt.toLocalDateTime().toDateTime().toDate().toString());
I don't understand why the output is minus one hour?
Original date: Sun Oct 23 11:00:00 BST 2011
Converted date: Sun Oct 23 11:00:00 BST 2011
You're using Date.toString() which always uses the local time zone. See how your string contains "BST"?
Ideally, stick to just Joda Time for as much of the time as you can:
Parse with the Joda Time formatters
Don't convert back to Date unless you need to
Don't use Date.toString() if you can possibly avoid it; you have no control over its format.
It's not clear what you're really trying to achieve, but you almost certainly don't want to do this many conversions. For example, you're calling toLocalDateTime() followed by toDateTime() again - which means it's using the system default time zone, after you'd carefully specified UTC in the previous conversion...
Your code contains the following conversions (in this order):
String to Date
Date to DateTime
DateTime to DateTime in UTC
DateTime to LocalDateTime (*)
LocalDateTime to DateTime
DateTime to Date
Date to String
(From the results at *) LocalDateTime to DateTime
DateTime to LocalDateTime
LocalDateTime to DateTime
DateTime to Date
Date to String
What do you think the chances of all those conversions being both necessary and correctly specified are? ;)
Original has changed because conversion to the UTC is done with respect to HOST time zone, so it should change.
Converted had changed, in fact it's the problem of accessing method.
You are getting base time and the modifier is stored in other field.
Try going into debugging mode and you will see that after conversion cvtldt
has toString with modifier.
Regards,
Grzesiek
Related
I'm using "Asia/Bangkok" zone id.
That offset is from GMT UTC+07:00.
but when I did followings, then it is not +7:00 when set "01/01/1900 7:00:00.000"
SimpleDateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss.SSS");
Date date = dateFormat.parse("01/01/1900 7:00:00.000");
System.out.println(date);
System.out.println(date.getTimezoneOffset());
Date date2 = dateFormat.parse("01/01/1900 6:00:00.000");
System.out.println(date2);
System.out.println(date2.getTimezoneOffset());
The result is
Mon Jan 01 07:00:00 ICT 1900
-402
Mon Jan 01 06:00:00 ICT 1900
-420
I wondered if the offset had changed around 7:00 a.m. on January 1, 1900, so I looked it up on Wikipedia.
https://en.wikipedia.org/wiki/Time_in_Thailand
It was UTC+6:42, but from 1880 to 1920.
I have 3 questions.
Why it happen different time offset between "01/01/1900 7:00:00.000" and "01/01/1900 6:00:00.000"
Where can I see time zone history in Java.
How can I ignore different time offset in same Timezone.
-- additional question --
I understand that I should use LocalDateTime.
What is the best way to ignore offset and convert Date to LocalDateTime?
For example, in the following case, the value of convertedDate2 was converted based on an offset of -402.
DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("MM/dd/yyyy H:mm:ss.SSS");
LocalDateTime originalLdate = LocalDateTime.parse("01/01/1900 7:00:00.000", dateFormatter);
LocalDateTime originalLdate2 = LocalDateTime.parse("01/01/1900 6:00:00.000", dateFormatter);
System.out.println(originalLdate);
System.out.println(originalLdate2);
SimpleDateFormat dateFormat = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss.SSS");
Date date = dateFormat.parse("01/01/1900 7:00:00.000");
Date date2 = dateFormat.parse("01/01/1900 6:00:00.000");
LocalDateTime convertedDate = date.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
LocalDateTime convertedDate2 = date2.toInstant().atZone(ZoneId.systemDefault()).toLocalDateTime();
System.out.println(convertedDate);
System.out.println(convertedDate2);
LocalDateTime convertedDate3 = LocalDateTime.parse(dateFormat.format(date), dateFormatter);
LocalDateTime convertedDate4 = LocalDateTime.parse(dateFormat.format(date2), dateFormatter);
System.out.println(convertedDate3);
System.out.println(convertedDate4);
The result is
1900-01-01T07:00
1900-01-01T06:00
1900-01-01T07:00
1900-01-01T05:42:04
1900-01-01T07:00
1900-01-01T06:00
If I convert it once to String and then to LocalDateTime, as in convertedDate3 and convertedDate4,
then I could convert as my expectation, but I wonder this is the most efficient way or not?
Java runtime timezone information for each version is available here
https://www.oracle.com/java/technologies/tzdata-versions.html
Inside the linked file (for a specific version) you can find links to the actual data used
https://www.iana.org/time-zones/repository/releases/tzcode2021a.tar.gz
https://www.iana.org/time-zones/repository/releases/tzdata2021a.tar.gz
https://www.iana.org/time-zones/repository/releases/tzdb-2021a.tar.lz
Inside the tzdata*.tar.gz you can find a file called asia which contains the data for Bangkok as well.
It contains these entries
# Thailand
# Zone NAME STDOFF RULES FORMAT [UNTIL]
Zone Asia/Bangkok 6:42:04 - LMT 1880
6:42:04 - BMT 1920 Apr # Bangkok Mean Time
7:00 - +07
Link Asia/Bangkok Asia/Phnom_Penh # Cambodia
Link Asia/Bangkok Asia/Vientiane # Laos
So the -402 timezone should be used for all dates before 1/4/1920, but it seems the implementation is using the -402 offset only from 1/1/1900 0:00:00.000 UTC (from 1/1/1900 6:42:04.000 in your timezone) and until 1/4/1920 in your timezone and -420 otherwise. I am not sure, if that is intended or a bug.
How can I ignore different time offset in same Timezone.
If you are actually using timezones in your application, then you should not ignore them.
However, if you are making an application that is intended to be used just in your local timezone, then you can use a DateTime class without timezone information, such as java.time.LocalDateTime.
Also worth noting: even if these timezones would be correct, the historical dates might still be inaccurate, due to modern time rules being applied for all time (see below). So in the end it depends on what your use case is.
A date-time without a time-zone in the ISO-8601 calendar system. The ISO-8601 calendar system is the modern civil calendar system used today in most of the world. It is equivalent to the proleptic Gregorian calendar system, in which today's rules for leap years are applied for all time. For most applications written today, the ISO-8601 rules are entirely suitable. However, any application that makes use of historical dates, and requires them to be accurate will find the ISO-8601 approach unsuitable.
java.util.Date and java.text.SimpleDateFormat are very old classes. Although they mostly work, they are difficult to use properly, especially where timezones are concerned.
Date.getTimezoneOffset is deprecated. Do not use deprecated methods.
The proper way to work with timezone rules is using the java.time, java.time.zone, and java.time.format packages:
ZoneId zone = ZoneId.systemDefault();
DateTimeFormatter dateFormatter =
DateTimeFormatter.ofPattern("MM/dd/yyyy H:mm:ss.SSS");
LocalDateTime date =
LocalDateTime.parse("01/01/1900 7:00:00.000", dateFormatter);
System.out.println(date);
System.out.println(zone.getRules().getOffset(date));
LocalDateTime date2 =
LocalDateTime.parse("01/01/1900 6:00:00.000", dateFormatter);
System.out.println(date2);
System.out.println(zone.getRules().getOffset(date2));
The entire history of a timezone is in the ZoneRules:
System.out.println();
zone.getRules().getTransitions().forEach(System.out::println);
System.out.println();
zone.getRules().getTransitionRules().forEach(System.out::println);
You also asked:
What is the best way to ignore offset and convert Date to LocalDateTime?
You can’t. It is not possible to convert a Date to a LocalDateTime without assuming a timezone.
A Date is a wrapper for the number of milliseconds since 1970-01-01 00:00:00 UTC. You cannot generate a LocalDateTime from that without knowing which timezone to apply to that millisecond count. For example, noon Eastern Time in the US is a different number of milliseconds since 1970 than noon Greenwich time.
You may not realize it, but when you use SimpleDateFormat, you are specifying a timezone. Every SimpleDateFormat has a timezone property. Since your code never set that timezone explicitly, your date format used the system’s default timezone.
That is one reason to avoid DateFormat and SimpleDateFormat: the implicit use of the default timezone leads to errors and confusing behavior (though it is predictable behavior). When you use the java.time package and its subpackages, there is no ambiguity, and far less chance of confusion.
I have a date time that I am first converting to local time, followed by a conversion to another time zone. The first conversion works with no issue however the second conversion is ignored. What is the issue?
String input = "2020-05-20 01:10:05";
SimpleDateFormat localFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
localFormat.setTimeZone(TimeZone.getTimeZone(ZoneId.systemDefault()));
try {
Date date = localFormat.parse(input);
System.out.println(date); //Wed May 20 01:10:05 PDT 2020 <--- Logs this (Expected)
SimpleDateFormat estFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
estFormat.setTimeZone(TimeZone.getTimeZone("America/New_York"));
String newDate = estFormat.format(date);
System.out.println(newDate); //2020-05-20 04:10:05 <--- Logs this (Expected)
Date dateEst = estFormat.parse(newDate);
System.out.println(dateEst); //Wed May 20 01:10:05 PDT 2020 <--- Logs this (Unexpected) Should be Wed May 20 04:10:05 EST 2020
}catch (Exception e){
e.printStackTrace();
}
It seems like the second estFormat.parse() is ignored when trying to convert to America/New_York time zone.
java.time
I warmly recommend that you use java.time, the modern Java date and time API, for your date and time work. Once you get used to the slightly different mindset, you will likely also find the resulting code clearer and more natural to read. Let’s first define the constant stuff as constants:
private static final DateTimeFormatter FORMATTER
= DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss", Locale.ROOT);
private static final ZoneId FROM_ZONE = ZoneId.of("America/Los_Angeles");
private static final ZoneId TO_ZONE = ZoneId.of("America/New_York");
With these we can do our work:
String input = "2020-05-20 01:10:05";
ZonedDateTime fromDateTime
= LocalDateTime.parse(input, FORMATTER).atZone(FROM_ZONE);
System.out.println("From: " + fromDateTime);
ZonedDateTime toDateTime = fromDateTime.withZoneSameInstant(TO_ZONE);
System.out.println("To: " + toDateTime);
String formatted = toDateTime.format(FORMATTER);
System.out.println("Formatted: " + formatted);
Output is:
From: 2020-05-20T01:10:05-07:00[America/Los_Angeles]
To: 2020-05-20T04:10:05-04:00[America/New_York]
Formatted: 2020-05-20 04:10:05
Edit:
How would I get it to have EST 2020 at the end?
A good option for most purposes is to use a localized formatter:
private static final DateTimeFormatter TARGET_FORMATTER
= DateTimeFormatter.ofLocalizedDateTime(FormatStyle.LONG)
.withLocale(Locale.US);
Like this:
String formatted = toDateTime.format(TARGET_FORMATTER);
Formatted: May 20, 2020 at 4:10:05 AM EDT
A detail, we didn’t get EST at the end because New York and most of the East coast of Northern America uses summer time (DST) and hence is on Eastern Daylight time, EDT, in May.
What went wrong?
It seems that you were expecting your Date object to carry the time zone of the formatter that parsed it, America/New_York. An old-fashioned Date object cannot do that. It’s just a dumb point in time without any time zone or other additional information. What confuses many is that its toString method uses the default time zone of the JVM to render the string returned, thus giving the false impression of a time zone being present. In contrast the modern ZonedDateTime, as the name says, does hold a time zone.
Link
Oracle tutorial: Date Time explaining how to use java.time.
First, don't use Date unless you're maintaining legacy code.
Second, SimpleDateFormat parsed the date correctly. You're not using estFormat to format the date as you did in the previous (correct) example. Try:
System.out.println(estFormat.format(dateEst));
This is a good overview of the different types of date-related entities in Java and is worthwhile reading. Here's an excerpt you may find useful:
The java.util.Date has no concept of time zone, and only represents the number of seconds passed since the Unix epoch time – 1970-01-01T00:00:00Z. But, if you print the Date object directly, the Date object will be always printed with the default system time zone.
I had noticed one thing the type of the first variable is String and the type of the Second variable is Date. So probably type conversion is creating a problem here. There is nothing like ignoring a second time.
I have a date format yyyy/mm/dd hh:mm:ss in GMT format. I want to convert the date from GMT format to BST time. What's the simplest way to do this?
With Java 8, the easiest way is probably to:
parse the date into a LocalDateTime
use it to create a ZonedDateTime using GMT time zone
change the time zone to BST
get the LocalDateTime of that new date
Sample example:
String date = "2015/03/09 10:32:00";
LocalDateTime gmt = LocalDateTime.parse(date, DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss"));
ZonedDateTime instant = ZonedDateTime.of(gmt, ZoneId.of("GMT"));
LocalDateTime bst = instant.withZoneSameInstant(ZoneId.of("Europe/London")).toLocalDateTime();
System.out.println(bst);
If you change the month to July, for example, you should see an offset of one hour as expected.
(I assumed that BST is British Summer Time - it could also be Bangladesh Standard Time: in general it is better to use the full name of the time zone to avoid ambiguities).
I try to convert a string into a datetime:
String dateString = "2015-01-14T00:00:00-04:00";
DateTimeFormatter df = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ssZ");
DateTime dt = df.parseDateTime(dateString);
If I display dt.toDate()
I get: Tue Jan 13 23:00:00 EST 2015
So there is a time problem.
Without the DateTimeFormatter, I get the same issue.
It's getting the correct value - basically 4am UTC, which is midnight in a UTC offset of -04:00 (as per the original text), or 11pm on the previous day for EST (as per the displayed result).
The problem is that you're using java.util.Date.toString(), which always returns the date in the system time zone. Note that a java.util.Date only represents an instant in time - it has no notion of a time zone itself, so its toString() method just uses the system default.
If you want to retain the time zone information (or in this case, the offset from UTC information - you don't have a full time zone) then stick to DateTime instead of converting to Date. Ideally, avoid java.util.Date/java.util.Calendar entirely. Stick to Joda Time and/or java.time.*.
I have a timestamp that I am trying to put into a Date object, however when I use Calendar, I am running into a strange problem. I seem to be able to unable to create a Date object with the values I want:
public static void main(String args[]){
Date today = new Date();
int hour = 4, min=0, sec=0, ms=64;
Calendar cal = GregorianCalendar.getInstance();
cal.clear();
cal.setTimeZone(TimeZone.getTimeZone("EDT"));
cal.setTime(today);
cal.set(Calendar.HOUR_OF_DAY,hour);
cal.set(Calendar.MINUTE,min);
cal.set(Calendar.SECOND,sec);
cal.set(Calendar.MILLISECOND,ms);
System.out.println("Time is: "+cal.getTime());
}
This produces:
Time is: Mon Jan 13 23:00:00 EST 2014
which is not the result I am looking for.
However, if I comment out the 'setTimeZone' method call, I get the following result:
Time is: Tue Jan 14 04:00:00 EST 2014
This is the result that I am looking for but I am concerned that if I am running on a machine that is not running in the same time zone, I will not get consistent behavior.
This is the result that I am looking for but I am concerned that if I am running on a machine that is not running in the same time zone
it is the problem. The internal representation should be ok, but it prints on local timezone: representation differs from real content.
use SimpleDateFormat http://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html and set TimeZone to see the date on the Zone desired.
The problem here is that Java does not know of the timezone "EDT" (Eastern Daylight Time). As a result, Calendar seems to be setting the timezone to GMT.
The timezone needed here is "America/New_York" or "EST5EDT". When either of these values are used, the correct result is produced.
The list of valid Time Zones can be obtained by calling TimeZone.getAvailableIDs()
It is unfortunate that no warnings are produced when the requested Time Zone is not found.
If you can do away with java.util.Date, you can use joda time API to conveniently set these values as desired:
For your query, you can set your already created Calendar instance as a constructor parameter to DateTime.
DateTime dt = new DateTime(cal);
System.out.println(dt.toDateTimeISO());
Output:
2014-01-14T04:00:00.064-05:00
Calendar.getTime() returns a java.util.Date object. Date objects do not know anything about timezones. The Date object that Calendar.getTime() returns does not know to what timezone the Calendar that it came from is set.
When you print a Date object (for example, by implicitly calling toString() object, as you are doing) it is formatted in the default time zone of the machine you are running it on.
If you want to print a Date in a specific timezone, use a SimpleDateFormat, and set the desired timezone on the SimpleDateFormat object. For example:
DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z");
df.setTimeZone(TimeZone.getTimeZone("EDT"));
// Will display the date that the calendar is set to in the EDT timezone
System.out.println(df.format(cal.getTime()));
Java Date objects represent the number of milliseconds seconds since January 1, 1970, 00:00:00 GMT due to the fact that the other methods are deprecated. The two ways to "view" a Date object directly are "getTime()" and "toString()" (using "dow mon dd hh:mm:ss zzz yyyy"). Therefore, you are formatting the GMT value to your local timezone.
When working with dates, it is best to think of them as GMT values, and then as a "formatting" exercise when viewing the date.
For comparison, here is that same kind of code but using Joda-Time 2.3.
Avoid the java.util.Date & .Calendar classes.
Never use three-letter codes for time zones. They are neither standardized nor unique. Instead use proper time zone names. In this case, use "America/New_York" or "America/Montreal".
// Use time zone names, such as from this slightly outdated list: http://joda-time.sourceforge.net/timezones.html
DateTimeZone timeZone = DateTimeZone.forID( "America/New_York" );
// Input.
int hour = 4, min = 0, sec = 0, ms = 64;
// Start with now, then adjust the time of day.
DateTime now = new DateTime( timeZone );
DateTime dateTime = now.withHourOfDay( hour ).withMinuteOfHour( min ).withSecondOfMinute( sec ).withMillisOfSecond( ms );
// If needed, translate to a java.util.Date for use with other classes.
java.util.Date date = dateTime.toDate();
Dump to console…
System.out.println( "now: " + now );
System.out.println( "dateTime: " + dateTime );
System.out.println( "date: " + date );
When run…
now: 2014-01-20T21:04:51.237-05:00
dateTime: 2014-01-20T04:00:00.064-05:00
date: Mon Jan 20 01:00:00 PST 2014