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How to Convert "2021-05-14T13:42:48.000Z" string to Date Object?

I am trying to convert "2021-05-14T13:42:48.000Z" string to Date Object.
I have tried this:
DateFormat dateFormat = new SimpleDateFormat("YYYY-MM-DDHH:MM:SS");
And also this, which i saw on stackoverflow only:-
DateFormat dateFormat = new SimpleDateFormat("YYYY-MM-DD'T'HH:MM:SS'A'");
But none of it worked.
How can i convert this string to my date object?

Assuming your date string always represents a UTC time (with the 'Z'), you can use format string:
yyyy-MM-dd'T'HH:mm:ss.SSSZ
but you'll first need to replace the Z in your date string with the fixed timezone "+0000", as in "2021-05-14T13:42:48.000+0000".
Try this:
String myDateString = "2021-05-14T13:42:48.000Z"
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ", Locale.US);
Date myDate = dateFormat.parse (myDateString.replace("Z","+0000"));
This will return a date correctly adjusted for your current timezone, in my case 9:42:48am EDT.
There is a more detailed discussion at Converting ISO 8601-compliant String to java.util.Date which you may find useful.

You have used the date-time format incorrectly. It's important to note that the date-time formats have different meanings between capitalized and small letters.
For example: Capital MM means months, whereas small mm means minutes.
To know more about the date formats, you can refer this:
https://cheatography.com/pezmat/cheat-sheets/date-time-formats/pdf/
or this:
https://devhints.io/datetime
And the answer for your case is:
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");

Please do not use SimpleDateFormat or even java.date. All these classes are deprecated.
Instead, rely on the Android available java.time package.
In short:
val source = "2021-05-14T13:42:48.000Z"
val parsed = ZonedDateTime.parse(source)
This will correctly parse the timezone (Z for Zulu/UTC/GMT).
You can verify this, by simply converting the parsed Zoned date time into, for example, Europe/Amsterdam time (which is +2).
val source = "2021-05-14T13:42:48.000Z"
val parsed = ZonedDateTime.parse(source)
parsed.toString() // prints: 2021-05-14T13:42:48Z
parsed.zone // prints: "Z"
ZoneId.of(parsed.zone.id) // returns the ZoneOffset "Z" (correct)
// Convert to Amsterdam Time
val amsterdamDateTime = parsed.withZoneSameInstant(ZoneId.of("Europe/Amsterdam"))
amsterdamDateTime.toString() // prints: 2021-05-14T15:42:48+02:00[Europe/Amsterdam] (2 hours ahead of the Zulu time, also correct).
parsed.format(DateTimeFormatter.ISO_DATE_TIME).toString() // Prints: 2021-05-14T13:42:48Z (correct)
So as you can see, these classes do the right thing (most of the time).
I suggest you use them.

Same Milliseconds values coming for different dates

I store my values in database by converting the date value in milliseconds,so to get the latest date on top by using order by desc query. The order is coming as required but if i enter date 02/01/2016 and 01/30/2016 both are storing same milliseconds value.
String date = "02/01/2016";
String month = date.substring(0, 2);
String day = date.substring(3, 5);
String year = date.substring(6, 10);
Calendar c1 = Calendar.getInstance();
c1.set(Integer.parseInt(year), Integer.parseInt(month), Integer.parseInt(day));
long left = c1.getTimeInMillis();
After debugging i got the following milliseconds values
02/01/2016----61414914600000
and 01/30/2016----61414914600000
Anybody knows why this happening?

Using SimpleDateFormat value I am getting different milliseconds value:
Date date;
String dtStart = "02/01/2016";
SimpleDateFormat format = new SimpleDateFormat("MM/dd/yyyy");
try {
date = format.parse(dtStart);
long timeMills=date.getTime();
System.out.println("Date ->" + date);
} catch (Exception e) {
e.printStackTrace();
}

I ran your initial code and it functions almost as expected. A few points:
You mention millisecond 61414914600000. That's not correct because it's 1900 years into the future:
http://currentmillis.com/?61414914600000
I'm pretty sure you got that number from a Date object, not from a Calendar: http://docs.oracle.com/javase/6/docs/api/java/util/Date.html#Date(int, int, int)
As Mat said the month is zero-based for Calendar and the line where you call the setter should subtract 1:
c1.set(Integer.parseInt(year), Integer.parseInt(month) - 1, Integer.parseInt(day));
You answered your own question with another snippet of code but Date is deprecated, Calendar should be used instead. Your original code in the initial post was essentially correct (except the zero-based month). You should make sure that you know where your output is coming from and / or that you don't forget to build the code before running it.

How to find out GMT offset value in android

How to find out the values of GMT for user for example it is +05:30 for India.
How do calculate this +05:30 value in Android ?
I need this because I am using a java library in my app which has a function with this +05:30 field and I want to generate this field by calculation so that I wont have to fill up individual values for countries.

This is what works awesome
public double getOffset(){
TimeZone timezone = TimeZone.getDefault();
int seconds = timezone.getOffset(Calendar.ZONE_OFFSET)/1000;
double minutes = seconds/60;
double hours = minutes/60;
return hours;
}

First get the epoch system time
System.currentTimeMillis()
Then use a date object, set the time zone to GMT and initialize with the long valye
dateObj.setTimeZone(TimeZone.getTimeZone("GMT"))

To get time in GMT use below function where dateInString is the value of date,and format is date format as yyyyMMddHH
public static long getDate(String dateInString,String format){
long date = 0;
SimpleDateFormat dateFormat = new SimpleDateFormat(format);
try {
dateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));
Date d = dateFormat.parse(dateInString);
date = d.getTime();
} catch (ParseException e) {
e.printStackTrace();
}
return date;
}

Use below method to get UTC :-
public int GetUnixTime()
{
Calendar calendar = Calendar.getInstance();
long now = calendar.getTimeInMillis();
int utc = (int)(now / 1000);
return (utc);
}
after you get UTC now compared it to the Epoch in this site http://www.xav.com/time.cgi.
see this below link :-
How can I get the current date and time in UTC or GMT in Java?

If you store a map between timezones and their GMT offsets in your app, you can call TimeZone.getDefault() to get the device's timezone and do a quick lookup to return the GMT offset. That way you don't have to rely on potentially tricky date/time calculations and can be sure you have the correct value.

Maximum digits in Base10 ASCII Representation of UTC Time in android

A 4 byte Long integer can give
(2^(32) - 1) = 4294967295
10 digit
Now, the time given by Location Manager in android is currently 13 digit long( like 1366588814000 ).
Can the number of digits increase in future as time progresses ? I don't know in what data type android stores the time.

The return type of the getTime() is long as mentioned in the docs. So you need not worry about the length of the digits. You can always convert that time to a human readable form like
long time = location.getTime();
Date date = new Date(time);
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String text = sdf.format(date);
System.out.println(text);

Getting number of days difference between 2 dates

I am using jxl api to read an excel file in android. When I get a date like "30/11/2012" from excel, the LabelCell output shows me date as "11/30/12".
1) I need to get the output in dd/MM/yyyy format when reading the excel file, because it exists that way in excel, so I wouldn't want to unnecessarily convert it into another format. How to do that ?
2) After reading in the excel column's date, I generate 2 variables, one which has excel date - 20 days (lets call it excelMinus20) and another excel date + 10 days (lets call it excelPlus10.
Now, I would like to check going further, if the current system date (smartphone's date) >= excelMinus20 and current system date <= excelPlus10.
How to do this whole thing using java.text.Date ? I tried using joda time as well, but it's too complicated to use. Please guide me at least in the right direction.
Thanks in advance
Omkar Ghaisas

To parse your date from text format:
DateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");
Date date = formatter.parse("30/11/2012");
More info : SimpleDateFormat doc
To substract days from your date:
public static Date substractDays(Date date, int days)
{
long millis = date.getTime();
long toSubstract = days * 1000 * 60 * 60 * 60 * 24;
// 1milli 1s 1m 1h 1d
return new Date(millis-toSubstract);
}
Adding some days would be the same, except replace - with +
To get back a String representation from a Date object:
DateFormat formatter = new SimpleDateFormat("...pattern...");
String formatedDate = formatter.format(date.getTime());
EDIT:
You could also do the Date adding/substracting with the method you suggested:
public static Date substractDays(Date date, int days)
{
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.add(Calendar.DATE, -20 /*or +10*/);
return calendar.getTime();
}
If you want to check if a Date is in an interval, then:
public static boolean isInInterval(Date date, Date from, Date to)
{
return date.getTime()<to.getTime() && date.getTime() > from.getTime();
}