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Get time from long value [duplicate]

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Android:Display time after adding GMT time zone
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I am converting milliseconds to the time of the respective country time format, for example, pakistan, US etc
For example
timeinmilliseconds=1549362600000
So its respective Time formate from which I got these milliseconds is 15:30 or 3:30 in 12 hr format
When I want to convert these milliseconds back to that time
I get 10:30 (Five hrs back)
public String getTimeFromLong(long timeInMilliseconds){
String mytime="";
long minute = (timeInMilliseconds / (1000 * 60)) % 60;
long hour = (timeInMilliseconds / (1000 * 60 * 60)) % 24;
mytime = String.format("%02d:%02d", hour, minute);
return mytime;
}
If I select time 4:00
I converted to that to milliseconds (This part is OK)
And wants the time back from milliseconds but get five hours back
For example, If I select time 9:30
convert it to milliseconds and then to time
I get 4:30

You need to use your local time zone to get the time in your region, the default is being apllied which is the Greenwich Mean Time (GMT). For Pakistan use Asia/Karachi like so:
SimpleDateFormat simpleDateFormat= new SimpleDateFormat("hh:mm");
simpleDateFormat.setTimeZone(TimeZone.getTimeZone("Asia/Karachi"));

Use this method to convert milliseconds into your local time
public String getTime(long time){
Calendar calendar = new GregorianCalendar();
calendar.setTimeInMillis(time);
SimpleDateFormat format = new SimpleDateFormat("hh:mm a");
Date date = new Date(time);
String kTime = format.format(date);
return kTime;
}

Using Java 8 we can do the following.
LocalDateTime dateTime =
LocalDateTime.ofInstant(Instant.ofEpochMilli(longValue), ZoneId.systemDefault());
to get date and time

Use below code to get time from long values:
public String getTimeFromLong(long timeInMilliseconds){
// Creating date format
DateFormat simple = new SimpleDateFormat("dd MMM yyyy HH:mm:ss:SSS Z");
Date result = new Date(timeInMilliseconds);
return simple.format(result);
}

How to add current time to a previous date in java?

I was trying to add current time into previous date. But it was adding in current date with time not with previous date.
see my bellow code:
Date startUserDate = ;//this is my previous date object;
startUserDate.setTime(new Date().getTime());// here i'm trying to add current time in previous date.
System.out.println("current time with previous Date :"+startUserDate);
In previous date there is no time and i want to add current time in previous date.I can do this, please help me out.

Use calendar object
Get instance of calendar object and set your past time to it
Date startUserDate = ;
Calendar calendar = Calendar.getInstance();
calendar.settime(startUserDate);
Create new calendar instance
Calendar cal = Calendar.getInstance();
cal.settime(new Date());
format the date to get string representation of time of current date
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
String currentdate = sdf.format(cal.getTime());
split that string to get hour minute and second object
String hh = expiry.split(":")[0];
String mm = expiry.split(":")[1];
String ss = expiry.split(":")[2];
add it to the previous calendar object
calendar .add(Calendar.HOUR_OF_DAY, hh);
calendar .add(Calendar.MINUTE, mm);
calendar .add(Calendar.SECOND, ss);
this date will have current time added to your date
Date newDate = calendar.getTime;

Use Calendar:
first set the date/time of the first calendar object to the old date
object use as second Calendar object to set the current time on the
first calendar object then convert it back to date
as follow:
//E.g. for startUserDate
Date startUserDate = new Date(System.currentTimeMillis() - (24L * 60L * 60L * 1000L) - (60L * 60L * 1000L));//minus 1 day and 1 hour
Calendar calDateThen = Calendar.getInstance();
Calendar calTimeNow = Calendar.getInstance();
calDateThen.setTime(startUserDate);
calDateThen.set(Calendar.HOUR_OF_DAY, calTimeNow.get(Calendar.HOUR_OF_DAY));
calDateThen.set(Calendar.MINUTE, calTimeNow.get(Calendar.MINUTE));
calDateThen.set(Calendar.SECOND, calTimeNow.get(Calendar.SECOND));
startUserDate = calDateThen.getTime();
System.out.println(startUserDate);
The second Calendar object calTimeNow can be replaced with Calendar.getInstance() where it is used.

You can do it using DateFormat and String, here's the solution that you need:
Code:
DateFormat df = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");
String timeString = df.format(new Date()).substring(10); // 10 is the beginIndex of time here
DateFormat df2 = new SimpleDateFormat("MM/dd/yyyy");
String startUserDateString = df2.format(startUserDate);
startUserDateString = startUserDateString+" "+timeString;
// you will get this format "MM/dd/yyyy HH:mm:ss"
//then parse the new date here
startUserDate = df.parse(startUserDateString);
Explanation:
Just convert the current date to a string and then extract the time from it using .substring() method, then convert your userDate to a string concatenate the taken time String to it and finally parse this date to get what you need.
Example:
You can see it working in this ideone DEMO.
Which takes 02/20/2002 in input and returns 02/20/2002 04:36:14 as result.

java.time
I recommend that you use java.time, the modern Java date and time API, for your date and time work.
ZoneId zone = ZoneId.systemDefault();
LocalDate somePreviousDate = LocalDate.of(2018, Month.NOVEMBER, 22);
LocalTime timeOfDayNow = LocalTime.now(zone);
LocalDateTime dateTime = somePreviousDate.atTime(timeOfDayNow);
System.out.println(dateTime);
When I ran the code just now — 16:25 in my time zone — I got this output:
2018-11-22T16:25:53.253892
If you’ve got an old-fashioned Date object, start by converting to a modern Instant and perform further conversion from there:
Date somePreviousDate = new Date(1_555_555_555_555L);
LocalDate date = somePreviousDate.toInstant().atZone(zone).toLocalDate();
LocalTime timeOfDayNow = LocalTime.now(zone);
LocalDateTime dateTime = date.atTime(timeOfDayNow);
2019-04-18T16:25:53.277947
If conversely you need the result as an old-fashioned Date, also convert over Instant:
Instant i = dateTime.atZone(zone).toInstant();
Date oldfasionedDate = Date.from(i);
System.out.println(oldfasionedDate);
Thu Nov 22 16:25:53 CET 2018
Link
Oracle tutorial: Date Time explaining how to use java.time.

The getTime method returns the number of milliseconds since 1970/01/01 so to get the time portion of the date you can either use a Calendar object or simply use modula arithmetic (using the above milliseconds value and the MAX millseconds in a day) to extract the time portion of the Date.
Then when you have the time you need to add it to the second date,
but seriously, use http://docs.oracle.com/javase/7/docs/api/java/util/Calendar.html
and use things like get (HOUR) and get (MINUTE) etc. which then you can use with set (HOUR, val)

You need to use Calendar class to perform addition to Dateobject. Date's setTime() will set that time in Date object but not add i.e it will overwrite previous date. new Date().getTime() will not return only time portion but time since Epoch. Also, how did you manipulated , startUserDate to not have any time (I mean , was it via Calendar or Formatter) ?
See Answer , Time Portion of Date to calculate only time portion,
long MILLIS_PER_DAY = 24 * 60 * 60 * 1000;
Date now = Calendar.getInstance().getTime();
long timePortion = now.getTime() % MILLIS_PER_DAY;
then you can use something like, cal.add(Calendar.MILLISECOND, (int)timePortion); where cal is Calendar object corresponding to your startUserDate in your code.

Calendar calendar = Calendar.getInstance();
calendar.setTime(startUserDate );
//new date for current time
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
String currentdate = sdf.format(new Date());
String hhStr = currentdate.split(":")[0];
String mmStr = currentdate.split(":")[1];
String ssStr = currentdate.split(":")[2];
Integer hh = 0;
Integer mm = 0;
Integer ss = 0;
try {
hh = Integer.parseInt(hhStr);
mm = Integer.parseInt(mmStr);
ss = Integer.parseInt(ssStr);
}catch(Exception e) {e.printStackTrace();}
calendar.set(Calendar.HOUR_OF_DAY, hh);
calendar.set(Calendar.MINUTE, mm);
calendar.set(Calendar.SECOND, ss);
startUserDate = calendar.getTime();

convert nanoseconds since 1904 to a valid java date

I have a number representing the number of nanoseconds since 12:00 a.m., January 1, 1904, universal time. I wish to instantiate a java.util.Date object representing that date. How should I proceed?

You first need to convert your number representing nanoseconds to milliseconds.
Then for the given date string, get the total number of milliseconds since the unix time Epoch, and then add the number earlier converted to milliseconds to it.
Here's the working code:
String target = "1904/01/01 12:00 AM"; // Your given date string
long nanoseconds = ...; // nanoseconds since target time that you want to convert to java.util.Date
long millis = TimeUnit.MILLISECONDS.convert(nanoseconds, TimeUnit.NANOSECONDS);
DateFormat formatter = new SimpleDateFormat("yyyy/MM/dd hh:mm aaa");
formatter.setTimeZone(TimeZone.getTimeZone("UTC"));
Date date = formatter.parse(target);
long newTimeInmillis = date.getTime() + millis;
Date date2 = new Date(newTimeInmillis);
System.out.println(date2);
Add an import java.util.concurrent.TimeUnit;.

I think it is trivial:
final GregorianCalendar startDate = new GregorianCalendar(TimeZone.getTimeZone("UTC"));
startDate.clear();
startDate.set(1904, Calendar.JANUARY, 1);
final long startMillis = startDate.getTimeInMillis();
new Date(nanos / 1000 / 1000 + startMillis)

Date date = new Date(new Date().getTime()-(time in nanoseconds/(1000*1000)));
what's wrong in using this? I tested with a value of "time in nanoseconds" for June 8th 1926 and it works. and date format has nothing to do with it, the underlying milliseconds value representing the time is what is required.

First of all java.util.Date
Allocates a Date object and initializes it so that it represents the time at which it was allocated, measured to the nearest millisecond.
So, if you have variable milliseconds
Somehow calculate number of milliseconds between your date and Jan 1, 1970 (Unix epoch) diff
Use Date(long) constructor
new Date(milliseconds - diff);

Milliseconds and nanoseconds in time format

This is my code:
long currentTime = System.currentTimeMillis();
Date date = new Date(currentTime); // if you really have long
String result = new SimpleDateFormat("HH:mm:ss").format(date.getTime());
Is it possible to add milliseconds and nanoseconds to the date format ?

You can add milliseconds by adding SSS at the end, such as the format will be HH:mm:ss.SSS.
There is no reference in the SimpleDateFormat to nanoseconds. Usually System.nanoTime() is used for performance debugging and not for display purposes.

String result = new SimpleDateFormat("HH:mm:ss:SSS").format(date);
"HH:mm:ss:SSS" //SSS stands for milliseconds
Check SimpleDateFormat API for more info

String timeStamp = new SimpleDateFormat("dd:MM:yyyy_HH:mm:ss:SSS").format(Calendar.getInstance().getTime());
timeStamp = timeStamp + ":" + System.nanoTime();
This gave me output,
24:03:2014_18:24:09:890:2018826751601473

How to convert 08:48 PM time into SQL unixtime?

How do I convert 08:48 PM formatted string into SQL Unixtime?
Java 1.5

You need java.text.SimpleDateFormat with the hh:mm a pattern (0-12 hours, minutes, AM/PM marker). Click the link to see the Javadoc with detailed pattern explanations.
String time = "08:48 PM";
Date date = new SimpleDateFormat("hh:mm a").parse(time);
long timestampMillis = date.getTime();
long unixTimestamp = timestampMillis / 1000;
If you actually want to store this in a SQL TIME/TIMESTAMP/DATETIME field with help of JDBC, then wrap it in a java.sql.Time and use PreparedStatement#setTime() to save it.
Time time = new Time(timestampMillis); // Yes, with millis!
preparedStatement.setTime(1, time);
// ...

Assuming you still want today's date, try
String today = new SimpleDateFormat("yyyy-MM-dd ").format(new Date());
long timestamp = new SimpleDateFormat("yyyy-MM-dd hh:mm a").parse(today + "08:48 PM").getTime() / 1000;