Develop Reference

Java - Convert From A Timezone Different From Local To UTC

So from all the posts I read about this issue (for example, Convert timestamp to UTC timezone).
I learn that a way to do this conversion is :
SimpleDateFormat dfmaputo = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss a");
dfmaputo.setTimeZone(TimeZone.getTimeZone("UTC"));
long unixtime = dfmaputo.parse(data.get(1)).getTime();
unixtime = unixtime / 1000;
output:
original date (Maputo Timezone) -- 11/5/2015 1:39:45 PM
unix timestamp in UTC --- 1446687585
data.get(1) is the string with the maputo datetime.
I don't understand why I'm not getting the UTC value. When I convert the unix timestamp, that I was expecting to be in UTC, I get the original datetime with Maputo Timezone.
Am I missing something?
Do I need to convert first to my local timezone and than to UTC?
EDIT: Solution
Calendar maputoDateTime = Calendar.getInstance(TimeZone.getTimeZone("Africa/Maputo"));
maputoDateTime.setTimeZone(TimeZone.getTimeZone("GMT"));
Long unixtimeGMT = maputoDateTime.getTimeInMillis() / 1000;
Instead of SimpleDateFormat I should use Calendar.
First I needed to set the input date's timezone (Africa/Maputo) and then set it to the one I needed (GMT). And only then I could get the correct unix timestamp.
Thanks to #BastiM reply in How to change TIMEZONE for a java.util.Calendar/Date
Thank you for your replies and help.

What if you add CAT timezone identifier to the end of string and formatter mask has z letter? If thats what you always get and source data does not give timezone value.
String sdt = "11/5/2015 11:39:45 PM CAT";
SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy hh:mm:ss a z", Locale.US);
Date dt = sdf.parse(sdt);
Calendar cal = Calendar.getInstance();
cal.setTimeInMillis(dt.getTime());
System.out.println(dt + ", utc=" + dt.getTime());
System.out.println(cal);

Oracle Date Format change to yyyy-MM-dd hh:mm:ss

I have date saletime as 2/25/14 22:06 I want to store it in oracle table in the yyyy-MM-dd hh:mm:ss. So I wrote following java code
Date saleTime = sale.getSaleTime();
logger.info("DateTime is "+saleTime);
SimpleDateFormat formatter=new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
Date saleTimeNorm = formatter.parse(formatter.format(saleTime));
logger.info("DateTime after Formating "+saleTimeNorm);
Timestamp oracleDate = new Timestamp(saleTimeNorm.getTime());
logger.info("New Format Inserting :"+oracleDate);
sale.setSaleTime(oracleDate);
But this seems to be giving :0014-02-25 22:06:00.0
Any suggestions ?

Your getSaleTime() method somehow regards "14" as a four-digit year, and returns the year 14.
After you have executed getSaleTime(), you already have a Date variable; there is no need (and no use) in converting it to a different output format and re-parsing the result. The Date you get from the calls to format() and parse() will be the same one you started with.
You can create your Timestamp using getTime() on the result of the call to getSaleTime(). That will be correct once you change getSaleTime() so that it returns the date in the correct year.

Something must be wrong in your sale.getSaleTime() method. Because the following code working as needed.
Date saleTime = Calendar.getInstance().getTime();
SimpleDateFormat formatter=new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
Date saleTimeNorm = formatter.parse(formatter.format(saleTime));
Timestamp oracleDate = new Timestamp(saleTimeNorm.getTime());
System.out.println(oracleDate);
//2014-05-13 03:58:53.0

Getting TimeZone instance from a date

With the following code-
Timestamp ts = (Timestamp)results.get(0);
SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss Z");
System.out.println(sdf.format(new Date(ts.getTime())));
I get output as: 04/29/2013 15:08:30 +0530
I wanted to create a TimeZone instance from the timestamp, so tried this-
SimpleDateFormat FORMATTER = new SimpleDateFormat("Z");
String tzString = FORMATTER.format(ts);
// the tzString comes out to be +0530 (which is correct)
TimeZone tz = TimeZone.getTimeZone(tzString);
System.out.println(tz);
But the final TimeZone instance is of GMT as its not able to identify +0530.
So, how can I get a correct TimeZone instance here?

You cannot get a TimeZone from a java.sql.Timestamp because it does not contain one. In your case you are simply getting your default TimeZone. It does not make sense. It is the same as TimeZone.getDefault();

Use a lowercase z in your pattern. That should return "GMT+0530", which will work.

Instead of using a SimpleDateFormat, you can simply do this:-
Calendar cal = Calendar.getInstance();
cal.setTime(new Date(ts.getTime()));
TimeZone tz = cal.getTimeZone();
System.out.println(tz);

I tried this code below:
Timestamp ts = new Timestamp(System.currentTimeMillis());
Then to get the TimeZone instance from the timestamp, I did this:
SimpleDateFormat FORMATTER = new SimpleDateFormat("Z");
TimeZone tzone = FORMATTER.getTimeZone();
System.out.println(tzone.getDisplayName());
System.out.println(tzone.getID());
I got:
Central European Time
Europe/Berlin
So I got my timezone which is +0200 instead of GMT.
Hope this is what you want.

Parsing date with different time zones

Even with about 15 years in Java one always stumbles over the topic of handling dates and times...
Here's the situation: I get a timestamp from some external system as a String representation. The timestamp's semantic is that it represents an UTC date. This timestamp has to be put in an entity and then into a PostgreSQL database in a TIMESTAMP field. Additionally I need to put the same timestamp as local time (in my case CEST) into the entity and then into the database in a TIMESTAMP WITH TIME ZONE field.
What is the right way to ensure that no matter what the settings of the machine executing the code are, the timestamps get stored correctly in the entity (to make some validations with other UTC timestamps) and in the database (to use them in reports later on)?
Here's the code, which worked fine on my local machine:
SimpleDateFormat sdfUTC = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS");
sdfUTC.setTimeZone(TimeZone.getTimeZone("UTC"));
Date utcTimestamp = sdfUTC.parse(utcTimestampString);
// getMachinesTimezone is some internal util method giving the TimeZone object of the machines Location
Calendar localTimestamp = new GregorianCalendar(getMachinesTimezone());
localTimestamp.setTimeInMillis(utcTimestamp.getTime());
But when executing the same code on the server, it resulted in different times, so I assume that it's not the correct way to handle it. Any suggestions?
PS: I read about Joda Time when searching in this forum, but in the given project I'm not able to introduce new libraries since I only change an existing module, so I have to live with the standard JDK1.6

If I understand correctly, You need to set the timezone on the same data/calendar object that you are printing. Like this:
private Locale locale = Locale.US;
private static final String[] tzStrings = {
"America/New_York",
"America/Chicago",
"America/Denver",
"America/Los_Angeles",
};
Date now = new Date();
for ( TimeZone z : zones) {
DateFormat df = new SimpleDateFormat("K:mm a,z", locale);
df.setTimeZone(z);
String result = df.format(now);
System.out.println(result);
}
if i set timezone to SimpleDateFormat it is working fine.
here is the sample code...
String date="05/19/2008 04:30 AM (EST)";
SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy hh:mm aaa (z)");
TimeZone.setDefault(TimeZone.getTimeZone("PST"));
long millis = sdf.parse(date).getTime();
sdf.setTimeZone(TimeZone.getDefault());
System.out.println(sdf.format(new Date(millis)));

I think you have to set the target time zone in you Calendar object. I think something like:
Calendar localTimestamp = new GregorianCalendar(TimeZone.getTimeZone("GMT+10"));
localTimestamp.setTimeInMillis(utcTimestamp.getTime());
In other case Java takes the default system time zone for the Calendar instance.

You can do it by the below example code.
Date date = new Date();
DateFormat formatter = new SimpleDateFormat("dd MMM yyyy HH:mm:ss z");
formatter.setTimeZone(TimeZone.getTimeZone("CET"));
Date date1 = dateformat.parse(formatter.format(date));
// Set the formatter to use a different timezone
formatter.setTimeZone(TimeZone.getTimeZone("IST"));
Date date2 = dateformat.parse(formatter.format(date));
// Prints the date in the IST timezone
// System.out.println(formatter.format(date));

Converting Epoch time to date string

I have seen this question asked multiple times and none of the answers seem to be what i need.
I have a long type variable which has an epoch time stored in it.
What i want to do is convert it to a String
for example if the epoch time stored was for today the final string would read:
17/03/2012
How would i to this?

Look into SimpleDateFormat
SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
sdf.format(new Date(myTimeAsLong));

You'd create a Date from the long - that's easy:
Date date = new Date(epochTime);
Note that epochTime here ought to be in milliseconds since the epoch - if you've got seconds since the epoch, multiply by 1000.
Then you'd create a SimpleDateFormat specifying the relevant pattern, culture and time zone. For example:
SimpleDateFormat format = new SimpleDateFormat("dd/MM/yyyy", Locale.US);
format.setTimeZone(...);
Then use that to format the date to a string:
String text = format.format(date);

Date date = new Date(String);
this is deprecated.
solution
Date date = new Date(1406178443 * 1000L);
DateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
format.setTimeZone(TimeZone.getTimeZone("Etc/UTC"));
String formatted = format.format(date);
make sure multiply by 1000L

If the method should be portable, better use the default (local time) TimeZone.getDefault():
String epochToIso8601(long time) {
String format = "yyyy-MM-dd HH:mm:ss";
SimpleDateFormat sdf = new SimpleDateFormat(format, Locale.getDefault());
sdf.setTimeZone(TimeZone.getDefault());
return sdf.format(new Date(time * 1000));
}

try this
Date date = new Date(1476126532838L);
DateFormat format = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
format.setTimeZone(TimeZone.getTimeZone("Etc/UTC"));
String formatted = format.format(date);
format.setTimeZone(TimeZone.getTimeZone("Asia/Colombo"));//your zone
formatted = format.format(date);
System.out.println(formatted);

Joda-Time
If by epoch time you meant a count of milliseconds since first moment of 1970 in UTC, then here is some example code using the Joda-Time library…
DateTimeZone timeZone = DateTimeZone.forID( "Europe/Paris" );
DateTime dateTime = new DateTime( yourMilliseconds, timeZone );
String output = DateTimeFormat.forStyle( "S-" ).withLocale( Locale.CANADA_FRENCH ).print( dateTime );
Other Epochs
That definition of epoch is common because of its use within Unix. But be aware that at least a couple dozen epoch definitions are used by various computer systems.

Time for someone to provide the modern answer (valid and recommended since 2014).
java.time
DateTimeFormatter formatter = DateTimeFormatter
.ofLocalizedDateTime(FormatStyle.LONG).withLocale(Locale.US);
String facebookTime = "1548410106047";
long fbt = Long.parseLong(facebookTime);
ZonedDateTime dateTime = Instant.ofEpochMilli(fbt).atZone(ZoneId.of("America/Indiana/Knox"));
System.out.println(dateTime.format(formatter));
The output is:
January 25, 2019 at 3:55:06 AM CST
If you wanted only the date and in a shorter format, use for example
DateTimeFormatter formatter = DateTimeFormatter
.ofLocalizedDate(FormatStyle.SHORT).withLocale(Locale.US);
1/25/19
Note how the snippet allows you to specify time zone, language (locale) and how long or short of a format you want.
Links
Oracle tutorial: Date Time explaining how to use java.time.
My example string was taken from this duplicate question

Try this...
sample Epoch timestamp is 1414492391238
Method:
public static String GetHumanReadableDate(long epochSec, String dateFormatStr) {
Date date = new Date(epochSec * 1000);
SimpleDateFormat format = new SimpleDateFormat(dateFormatStr,
Locale.getDefault());
return format.format(date);
}
Usability:
long timestamp = Long.parseLong(engTime) / 1000;
String engTime_ = GetHumanReadableDate(timestamp, "dd-MM-yyyy HH:mm:ss aa");
Result:
28-10-2014 16:03:11 pm

You need to be aware that epoch time in java is in milliseconds, while what you are converting may be in seconds. Ensure that both sides of the conversions are in milliseconds, and then you can fetch the date parameters from the Date object.

ArLiteDTMConv Utility help converting EPOUCH-UNIX Date-Time values, Form EPOUCH-UNIX-To-Date-format and Vise-Versa. You can set the result to a variable and then use the variable in your script or when passing as parameter or introduce in any DB criteria for both Window and Linux. (Download a zip file on this link)