String-Date conversion with nanoseconds - java

I've been struggling for a while with this piece of code for an Android app and I can't get the hang of it. I've read and tried every solution I found on stackoverflow and other places, but still no luck.
What I want to do is have a function to convert a string like "17.08.2012 05:35:19:7600000" to a UTC date and a function that takes an UTC date and converts it to a string like that.
String value = "17.08.2012 05:35:19:7600000";
DateFormat df = new SimpleDateFormat("dd.MM.yyyy HH:mm:ss:SSSSSSS");
try
{
Date today = df.parse(value);
System.out.println("Today = " + df.format(today) + " " + today.toGMTString());
}
catch (ParseException e)
{
e.printStackTrace();
}
This results in : Today = 17.08.2012 07:41:59:0000000 17 Aug 2012 04:41:59 GMT which are both wrong.
I tried setting SDF's timezone to UTC, no luck.
Another thing that I noticed: if I do df.setLenient(false);
It gives me : java.text.ParseException: Unparseable date: "17.08.2012 05:35:19:7600000" .
If anyone can provide me with some explanations / sample code, I would be very grateful. Thanks in advance

The result you are getting is absolutely right.
Let's analyze this:
17.08.2012 05:35:19:7600000
17: Day of month (17th)
08: Month of year (August)
2012: Year (2012)
05: Hour of day (5am)
35: Minute of hour (:35)
19: Second of minute (:19)
7600000: Milliseconds of second (7,600,000)
Now, the way the VM sees this is that you are declaring the time of day as 5:35:19am, then adding 7,600,000 milliseconds to it. 7,600,000 milliseconds = 7,600 seconds = 2 hours, 6 minutes, 40 seconds. 5:35:19am + 02:06:40 = 7:41:59am (and 0 milliseconds). This is the result you are getting. (It also appears that you are not setting the timezone properly, so the GMT string is 3 hours behind your result.)
If you want to retain the :7600000, to my knowledge this is not possible. As this can be simplified into seconds, the VM will automatically reduce it into the other time increments. The milliseconds (the SSSS) should be for storing values <1000.
I'd suggest you create a new SimpleDateFormat for your output; but remember that the milliseconds will be absorbed into the other times (since they are all stored as a single long in the Date object).

private String convertDate(String cdate)
{
SimpleDateFormat dateFormat = new SimpleDateFormat("dd.MM.yyyy HH:mm:ss:SSSSSSS");
SimpleDateFormat postFormater = new SimpleDateFormat("yyyy-MM-dd");
Date convertedDate;
try
{
convertedDate = dateFormat.parse(cdate);
cdate = postFormater.format(convertedDate);
}
catch (ParseException e)
{
Toast.makeText(getApplicationContext(),e.toString(),Toast.LENGTH_SHORT).show();
}
return cdate;
}
Try this.

This is what you need (but it will loose millisecond information):
"dd.MM.yyyy HH:mm:ss.'000000'"
If you used "dd.MM.yyyy HH:mm:ss.SSSSSS", then would get three leading zeros for your milliseconds.
If you used "dd.MM.yyyy HH:mm:ss.SSS'000'", then you could format a date, but not parse any date.
Try it out:
public static void main(String[] args) throws ParseException {
printDate("dd.MM.yyyy HH:mm:ss.SSS");//02.05.2010 21:45:58.073
printDate("dd.MM.yyyy HH:mm:ss.SSSSSS");//02.05.2010 21:45:58.000073
printDate("dd.MM.yyyy HH:mm:ss.SSS'000'");//02.05.2010 21:45:58.073000
printDate("dd.MM.yyyy HH:mm:ss.'000000'");//02.05.2010 21:45:58.000000
tryToParseDate("dd.MM.yyyy HH:mm:ss.SSS");//good
tryToParseDate("dd.MM.yyyy HH:mm:ss.SSSSSS");//good
tryToParseDate("dd.MM.yyyy HH:mm:ss.SSS'000'");//bad
tryToParseDate("dd.MM.yyyy HH:mm:ss.'000000'");//good
}
private static void printDate(String formatString) {
Date now = new Date();
SimpleDateFormat format = new SimpleDateFormat(formatString);
String formattedDate = format.format(now);
// print that date
System.out.println(formattedDate);
}
private static void tryToParseDate(String formatString) {
Date now = new Date();
SimpleDateFormat format = new SimpleDateFormat(formatString);
String formattedDate = format.format(now);
// try to parse it again
try {
format.parse(formattedDate);
System.out.println("good");
} catch (ParseException e) {
System.out.println("bad");
}
}

To drop the nanoseconds, use:
new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.")

Update: java.time
The Question and other Answers use terrible date-time classes that are now legacy. These flawed classes were years ago supplanted by the modern java.time classes defined in JSR 310. Avoid Calendar, DateFormat, Date, etc.
Define a formatting pattern with DateTimeFormatter.
String input = "17.08.2012 05:35:19:7600000";
DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd.MM.uuuu HH:mm:ss:SSSSSSS" );
Parse.
LocalDateTime ldt = LocalDateTime.parse( input , f ) ;
A LocalDateTime object represents a date with a time of day, but lacks the context of a time zone or offset from UTC.
If you are certain the input text is intended to represent a moment as seen in UTC, having an offset of zero hours-minutes-seconds, then assign a ZoneOffset to produce an OffsetDateTime object.
OffsetDateTime odt = ldt.atOffset( ZoneOffset.UTC ) ;
See this code run live at Ideone.com.
ISO 8601
I suggest you educate the publisher of your data about the use of ISO 8601 standard formats when serializing date-time values to text.
The java.time classes use ISO 8601 formats by default when parsing/generating text.

Related

Calculate Number of Days between Given time in ISO format and Current time

I have to find out number of days between a given Time and current time. Given time is in ISO format and one example is "2021-01-14 16:23:46.217-06:00".
I have tried it using "java.text.SimpleDateFormat" but it's not giving me accurate results.
In Below Given date, for today's time I am getting output as "633" Days which isn't correct. somehow after parsing it is taking date as "21 december 2020" which isn't correct
String TIMESTAMP_FORMAT = "YYYY-MM-DD hh:mm:ss.s-hh:mm" ;
int noOfDays = Utility.getTimeDifferenceInDays("2021-01-14 16:23:46.217-06:00", TIMESTAMP_FORMAT);
public static int getTimeDifferenceInDays(String timestamp, String TIMESTAMP_FORMAT) {
DateFormat df = new SimpleDateFormat(TIMESTAMP_FORMAT);
try {
Date date = df.parse(timestamp);
long timeDifference = (System.currentTimeMillis() - date.getTime());
return (int) (timeDifference / (1000*60*60*24));
} catch (ParseException e) {
e.printStackTrace();
}
return 0;
}
Looking for a better solution which gives me correct number of days. Thanks
Use java.time API
Classes Date and SimpleDateFormat are legacy.
Since Java 8 (which was released 10 years ago) we have a new Time API, represented by classes from the java.time package.
To parse and format the data, you can use DateTimeFormatter. An instance of DateTimeFormatter can be obtained via static method ofPattern(), or using DateTimeFormatterBuilder.
ofPattern():
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSSXXX");
DateTimeFormatterBuilder:
DateTimeFormatter formatter = new DateTimeFormatterBuilder()
.appendPattern("yyyy-MM-dd HH:mm:ss.") // main date-time part
.appendValue(ChronoField.MILLI_OF_SECOND, 3) // fraction part of second
.appendOffset("+HH:MM", "+00:00") // can be substituted with appendPattern("zzz") or appendPattern("XXX")
.toFormatter();
The string "2021-01-14 16:23:46.217-06:00", which you've provided as an example, contains date-time information and UTC offset. Such data can be represented by OffsetDateTime.
To get the number of days between two temporal objects, you can use ChronoUnit.between() as #MC Emperor has mentioned in the comments.
That's how the whole code might look like:
String toParse = "2021-01-14 16:23:46.217-06:00";
OffsetDateTime dateTime = OffsetDateTime.parse(toParse, formatter);
System.out.println("parsed date-time: " + dateTime);
Instant now = Instant.now();
long days = ChronoUnit.DAYS.between(dateTime.toInstant(), now);
System.out.println("days: " + days);
Output:
parsed date-time: 2021-01-14T16:23:46.217-06:00
days: 615
Note that since in this case you need only difference in days between the current date instead of OffsetDateTime you can use LocalDateTime, UTC offset would be ignored while parsing a string. If you decide to do so, then the second argument passed to ChronoUnit.between() should be also of type LocalDateTime.

convert string to date object give sunday web, GMT 00+ time i need in date formate dd/mm/yyyy

I am converting string to date object i have string like
2017/3/30. when i parse into date object it gives
sunday web, GMT 03 00:00:00 GMT+05:00 2019
Code is
String dob = "2017/3/30";
SimpleDateFormat format = new SimpleDateFormat("yyyy/dd/MM");
try {
startDate = format.parse(dob);
endDate = format.parse(formattedDate);
} catch (ParseException e) {
e.printStackTrace();
}
I need same formate in date object not string .
You need to format it again after parsing
new SimpleDateFormat("yyyy/dd/MM").format(date);
The 'format' method returns a String object from a Date object according to the pattern you specified. What you need is the .parse(String) method, which returns a Date from a String.
SimpleDateFormat sdf = new SimpleDateFormat("yyyy/dd/MM");
String yourDate = "2017/03/30";
try {
Date startDate = sdf.parse(yourDate);
} catch (ParseException e) {
e.printStackTrace();
}
Note that you have to comply with the given pattern, your date must be "2017/03/30". Hope this helps.
I think your problem is that your actual date format, 2017/3/30, does not agree with the format string you are giving to your SimpleDateFormat, yyyy/dd/MM. The first has the month in the middle and the day-of month last; the latter has got them the other way around. Therefore the Date you get from dob is the 3rd of June, 2019 (I think this is what you were trying to say, it wasn’t 100 % clear). SimpleDateFormat is understanding your dob as the 3rd day of the 30th month of 2017; when there are only 12 months in a year it just continues counting months into 2018 and 2019. It is quite lenient about the values supplied.
You just need to decide on the order of day, month and year. Your question (with the title) mentions 3 different orders, dd/mm/yyyy, 2017/3/30 and yyyy/dd/MM. Once you’re being consistent, your problems will be solved, I expect.
In most cases we don’t want to let bugs like this one slip through unnoticed. The solution to this is
format.setLenient(false);
After this call, your date format will no longer accept 30 as a month number, and will report your error back to you so you know and can correct it (and may not need to ask on Stack Overflow :-)
Stop using troublesome old date-time classes that are now legacy, supplanted by the java.time classes.
For a date-only value, parse as LocalDate.
String input = "2017/3/30";
DateTimeFormatter f = DateTimeFormatter.ofPattern( "uuuu/m/d" );
LocalDate ld = LocalDate.parse( input , f );
To assign the first moment of the day, specify a time zone.
ZoneId z = ZoneId.of( "America/Montreal" ) ;
ZonedDateTime zdt = ld.atStartOfDay( z );
To generate strings representing these values use DateTimeFormatter. This has been covered hundreds of times already. So search Stack Overflow for more examples and more discussions.
String output = ld.format( f );

Convert Java String with GMT date and -6 at end to CST [duplicate]

This question already has answers here:
Date and time conversion to some other Timezone in java
(11 answers)
Closed 8 years ago.
I have a string with gmt date value and -06:00 at end. What is best way to convert this to CST? I looked at other questions but none of them have -06:00 at end to answer my question.
This is what I tried and it errors out as java.text.ParseException: Unparseable date: "2015-02-19T11:50:09.5953377-06:00"
private DateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss:SSSSSSS'Z'");
private DateFormat gmtFormat = new SimpleDateFormat();
private TimeZone cstTime = TimeZone.getTimeZone("CST");
gmtFormat.setTimeZone(cstTime);
sdf.setTimeZone(TimeZone.getTimeZone("GMT"));
try {
System.out.println("cst start date is " + gmtFormat.format("2015-02-19T11:50:09.5953377-06:00"));
} catch (ParseException e) {
e.printStackTrace();
}
I've run into similar problems before, where I was actually getting dates in 3 different iso formats like that, and was pretty frustrated with it... This isn't pretty, but it may help point you in the right direction...
The 3 formats I was getting the info in:
private static final String ISO_FORMAT = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";
private static final String ISO_FORMAT2 = "yyyy-MM-dd'T'HH:mm:ss'Z'";
private static final String ISO_FORMAT3 = "yyyy-MM-dd'T'HH:mm:ss.SSSZ";
Actually attempting to parse them (without having to figure out the correct type beforehand, returning a new Date Object in the event all 3 failed so shit doesn't crash because of a damn date formatting exception):
public static Date parseIso(String date){
SimpleDateFormat sdf = new SimpleDateFormat(ISO_FORMAT, Locale.US);
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
try {
return sdf.parse(date);
}
catch (ParseException e) {
Log.g(TAG, "Failed 1st date parse with " + ISO_FORMAT + " for " + date);
sdf = new SimpleDateFormat(ISO_FORMAT2, Locale.US);
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
try {
return sdf.parse(date);
}
catch (ParseException e2) {
Log.g(TAG, "Failed 2nd date parse with " + ISO_FORMAT2 + " for " + date);
sdf = new SimpleDateFormat(ISO_FORMAT3, Locale.US);
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
try {
return sdf.parse(date);
}
catch (ParseException e3) {
Log.g(TAG, "Failed 3rd date parse with " + ISO_FORMAT3 + " for " + date);
}
}
}
return new Date();
}
And then for actually converting that date to a localized date:
public static String format(long mils, String format){
return format(getInstance(mils), format);
}
public static String format(Calendar calendar, String format){
SimpleDateFormat sdf = new SimpleDateFormat(format, Locale.US);
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
return sdf.format(new Date(calendar.getTime().getTime() + TimeZone.getDefault().getOffset(new Date().getTime())));
}
public static Calendar getInstance(long timeInMils){
Calendar cal = Calendar.getInstance();
cal.setTimeZone(TimeZone.getTimeZone("UTC"));
cal.setTimeInMillis(timeInMils);
return cal;
}
So now you can basically call
CalendarHelper.format(myDateObject.getTime(), "MMM dd, yyyy");
and it will return the localized, formatted date from the original UTC date you received.
Again, not pretty, but I hope this can point you in the right direction for converting between the UTC and client's time zone. Best of luck~
PS. I think ISO_FORMAT_3 is the one that will actually help you. I guess I probably could have started with that information, but I'm not a bright man.
ISO 8601
You seem to misunderstand the meaning of the input string, 2015-02-19T11:50:09.5953377-06:00. You do not have a "gmt date value".
That format appears to be the standard ISO 8601 format.
The T in the middle separates the date portion from the time-of-day portion.
The -06:00 at the end is an offset from UTC. It means "the date-time value shown here is six hours behind UTC".
CST
So, if by CST you mean Central Time Zone (some of the middle parts of the Americas continents), then you need have no conversion to perform. That string with the time 11:50 means "almost noon in Illinois, Arkansas, and Louisiana". If you add 6 hours to 11:50, you would learn the UTC (GMT) date-time at that same moment: 17:50 on same date.
Avoid 3-4 Letter Codes
By the way, avoid using three or four letter time zone codes such as "CST". Those codes are not standardized nor unique. Many duplicates exist. For example, take CST:
Central Standard Time (Americas)
China Standard Time
Central Standard Time (Australia)
Central Summer Time (Australia)
Cuba Standard Time
Instead use proper time zones. Most of these are continent plus a slash plus a city/region. Examples: America/Regina, America/Monterrey, and America/Indiana/Knox.
Joda-Time | java.time
The java.util.Date/.Calendar classes are notoriously troublesome. Avoid them.
Use either the Joda-Time library or the new java.time package built into Java 8. The java.time package is inspired by Joda-Time but is re-architected. Each has its own strengths and weaknesses.
Both Joda-Time and java.time use ISO 8601 formats as their defaults for both parsing and generating string representations of date-time values.
As this Question is really a duplicate with hundreds of such Questions and Answers already posted, I'll give just one quick example.
String input = "2015-02-19T11:50:09.5953377-06:00";
DateTimeZone zoneAmerica_Regina = DateTimeZone.forID( "America/Regina" );
DateTime dateTimeAmericaRegina = new DateTime( input, zoneAmerica_Regina );
DateTime dateTimeLosAngeles = dateTimeAmericaRegina.withZone( DateTimeZone.forID( "America/Los_Angeles" ) );
DateTime dateTimeUtc = dateTimeAmericaRegina.withZone( DateTimeZone.UTC );
Fractional Seconds
Your input string has a very small fraction of a second. Joda-Time (like java.util.Date) handles only millisecond resolution — three digits after the decimal point. The java.item package handles nanosecond resolution. Some systems use microsecond resolution, such as database like Postgres. And some systems follow the old Unix convention of whole seconds.

How can I convert a date in YYYYMMDDHHMMSS format to epoch or unix time?

EDIT: I have edited my question to include more information, I have tried many ways to do this already, asking a question on StackOverflow is usually my last resort. Any help is greatly appreciated.
I have a date (which is a Timestamp object) in a format of YYYYMMDDHHMMSS (e.g. 20140430193247). This is sent from my services to the front end which displays it in the format: date:'dd/MM/yyyy' using AngularJS.
How can I convert this into Epoch/Unix time?
I have tried the duplicate question that is linked to this, what I get returned is a different date.
I have also tried the following:
A:
//_time == 20140430193247
return _time.getTime()/1000; // returns 20140430193 - INCORRECT
B:
return _time.getTime(); // returns 20140430193247 (Frontend: 23/03/2608) - INCORRECT
C:
Date date = new Date();
//_time = 20140501143245 (i.e. 05/01/2014 14:32:45)
String str = _time.toString();
System.out.println("Time string is " + str);
//Prints: Time string is 2608-03-24 15:39:03.245 meaning _time.toString() cannot be used
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
try {
date = df.parse(str);
} catch (ParseException e) {
}
return date; // returns 20140501143245 - INCORRECT
D:
date = new java.sql.Date(_time.getTime());
return date; // returns 2608-03-24 - INCORRECT
The following shows the todays date correctly:
Date date = new Date();
return date; // returns 1398939384523 (Frontend: 01/05/2014)
Thanks
I got the answer after quite a while of trying different ways. The solution was pretty simple - to parse the time to a string as toString() didn't work.
Date date;
SimpleDateFormat df = new SimpleDateFormat("yyyyMMddHHmmss");
try {
date = df.parse(String.valueOf(_time.getTime()));
} catch (ParseException e) {
throw new RuntimeException("Failed to parse date: ", e);
}
return date.getTime();
tl;dr
LocalDateTime
.parse(
"20140430193247" ,
DateTimeFormatter.ofPattern( "uuuuMMddHHmmss" )
)
.atOffset(
ZoneOffset.UTC
)
.toEpochSecond()
java.time
Parse your input string as a LocalDateTime as it lacks an indicator of offset-from-UTC or time zone.
String input = "20140430193247" ;
DateTimeFormatter f = DateTimeFormatter.ofPattern( "uuuuMMddHHmmss" ) ;
LocalDateTime ldt = LocalDateTime.parse( input , f ) ;
Now we have a date with time-of-day, around half-past 7 PM on April 30 of 2014. But we lack the context of offset/zone. So we do not know if this was 7 PM in Tokyo Japan or 7 PM in Toledo Ohio US, two different moments that happened several hours apart.
To determine a moment, you must know the intended offset/zone.
If you know for certain that an offset of zero, or UTC itself, was intended, apply the constant ZoneOffset.UTC to get an OffsetDateTime.
OffsetDateTime odt = ldt.atOffset( ZoneOffset.UTC ) ;
How can I convert this into Epoch/Unix time?
Do you mean a count of seconds or milliseconds since the first moment of 1970 in UTC?
For a count of whole seconds since 1970-01-01T00:00Z, interrogate the OffsetDateTime object.
long secondsSinceEpoch = odt.toEpochSecond() ;
For milliseconds, extract a Instant object. An Instant represents a moment in UTC, and is the basic building-block class of java.time. Then interrogate for the count.
Instant instant = odt.toInstant() ;
long millisSinceEpoch = instant.toEpochMilli() ;

Convert java.util.Date to String

I want to convert a java.util.Date object to a String in Java.
The format is 2010-05-30 22:15:52
Convert a Date to a String using DateFormat#format method:
String pattern = "MM/dd/yyyy HH:mm:ss";
// Create an instance of SimpleDateFormat used for formatting
// the string representation of date according to the chosen pattern
DateFormat df = new SimpleDateFormat(pattern);
// Get the today date using Calendar object.
Date today = Calendar.getInstance().getTime();
// Using DateFormat format method we can create a string
// representation of a date with the defined format.
String todayAsString = df.format(today);
// Print the result!
System.out.println("Today is: " + todayAsString);
From http://www.kodejava.org/examples/86.html
Format formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String s = formatter.format(date);
Commons-lang DateFormatUtils is full of goodies (if you have commons-lang in your classpath)
//Formats a date/time into a specific pattern
DateFormatUtils.format(yourDate, "yyyy-MM-dd HH:mm:SS");
tl;dr
myUtilDate.toInstant() // Convert `java.util.Date` to `Instant`.
.atOffset( ZoneOffset.UTC ) // Transform `Instant` to `OffsetDateTime`.
.format( DateTimeFormatter.ISO_LOCAL_DATE_TIME ) // Generate a String.
.replace( "T" , " " ) // Put a SPACE in the middle.
2014-11-14 14:05:09
java.time
The modern way is with the java.time classes that now supplant the troublesome old legacy date-time classes.
First convert your java.util.Date to an Instant. The Instant class represents a moment on the timeline in UTC with a resolution of nanoseconds (up to nine (9) digits of a decimal fraction).
Conversions to/from java.time are performed by new methods added to the old classes.
Instant instant = myUtilDate.toInstant();
Both your java.util.Date and java.time.Instant are in UTC. If you want to see the date and time as UTC, so be it. Call toString to generate a String in standard ISO 8601 format.
String output = instant.toString();
2014-11-14T14:05:09Z
For other formats, you need to transform your Instant into the more flexible OffsetDateTime.
OffsetDateTime odt = instant.atOffset( ZoneOffset.UTC );
odt.toString(): 2020-05-01T21:25:35.957Z
See that code run live at IdeOne.com.
To get a String in your desired format, specify a DateTimeFormatter. You could specify a custom format. But I would use one of the predefined formatters (ISO_LOCAL_DATE_TIME), and replace the T in its output with a SPACE.
String output = odt.format( DateTimeFormatter.ISO_LOCAL_DATE_TIME )
.replace( "T" , " " );
2014-11-14 14:05:09
By the way I do not recommend this kind of format where you purposely lose the offset-from-UTC or time zone information. Creates ambiguity as to the meaning of that string’s date-time value.
Also beware of data loss, as any fractional second is being ignored (effectively truncated) in your String’s representation of the date-time value.
To see that same moment through the lens of some particular region’s wall-clock time, apply a ZoneId to get a ZonedDateTime.
ZoneId z = ZoneId.of( "America/Montreal" );
ZonedDateTime zdt = instant.atZone( z );
zdt.toString(): 2014-11-14T14:05:09-05:00[America/Montreal]
To generate a formatted String, do the same as above but replace odt with zdt.
String output = zdt.format( DateTimeFormatter.ISO_LOCAL_DATE_TIME )
.replace( "T" , " " );
2014-11-14 14:05:09
If executing this code a very large number of times, you may want to be a bit more efficient and avoid the call to String::replace. Dropping that call also makes your code shorter. If so desired, specify your own formatting pattern in your own DateTimeFormatter object. Cache this instance as a constant or member for reuse.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "uuuu-MM-dd HH:mm:ss" ); // Data-loss: Dropping any fractional second.
Apply that formatter by passing the instance.
String output = zdt.format( f );
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old date-time classes such as java.util.Date, .Calendar, & java.text.SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to java.time.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations.
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport and further adapted to Android in ThreeTenABP (see How to use…).
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time.
Altenative one-liners in plain-old java:
String.format("The date: %tY-%tm-%td", date, date, date);
String.format("The date: %1$tY-%1$tm-%1$td", date);
String.format("Time with tz: %tY-%<tm-%<td %<tH:%<tM:%<tS.%<tL%<tz", date);
String.format("The date and time in ISO format: %tF %<tT", date);
This uses Formatter and relative indexing instead of SimpleDateFormat which is not thread-safe, btw.
Slightly more repetitive but needs just one statement.
This may be handy in some cases.
Why don't you use Joda (org.joda.time.DateTime)?
It's basically a one-liner.
Date currentDate = GregorianCalendar.getInstance().getTime();
String output = new DateTime( currentDate ).toString("yyyy-MM-dd HH:mm:ss");
// output: 2014-11-14 14:05:09
It looks like you are looking for SimpleDateFormat.
Format: yyyy-MM-dd kk:mm:ss
In single shot ;)
To get the Date
String date = new SimpleDateFormat("yyyy-MM-dd", Locale.getDefault()).format(new Date());
To get the Time
String time = new SimpleDateFormat("hh:mm", Locale.getDefault()).format(new Date());
To get the date and time
String dateTime = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss", Locale.getDefaut()).format(new Date());
Happy coding :)
public static String formateDate(String dateString) {
Date date;
String formattedDate = "";
try {
date = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss",Locale.getDefault()).parse(dateString);
formattedDate = new SimpleDateFormat("dd/MM/yyyy",Locale.getDefault()).format(date);
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return formattedDate;
}
If you only need the time from the date, you can just use the feature of String.
Date test = new Date();
String dayString = test.toString();
String timeString = dayString.substring( 11 , 19 );
This will automatically cut the time part of the String and save it inside the timeString.
Here are examples of using new Java 8 Time API to format legacy java.util.Date:
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss:SSS Z")
.withZone(ZoneOffset.UTC);
String utcFormatted = formatter.format(date.toInstant());
ZonedDateTime utcDatetime = date.toInstant().atZone(ZoneOffset.UTC);
String utcFormatted2 = utcDatetime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss:SSS Z"));
// gives the same as above
ZonedDateTime localDatetime = date.toInstant().atZone(ZoneId.systemDefault());
String localFormatted = localDatetime.format(DateTimeFormatter.ISO_ZONED_DATE_TIME);
// 2011-12-03T10:15:30+01:00[Europe/Paris]
String nowFormatted = LocalDateTime.now().toString(); // 2007-12-03T10:15:30.123
It is nice about DateTimeFormatter that it can be efficiently cached as it is thread-safe (unlike SimpleDateFormat).
List of predefined fomatters and pattern notation reference.
Credits:
How to parse/format dates with LocalDateTime? (Java 8)
Java8 java.util.Date conversion to java.time.ZonedDateTime
Format Instant to String
What's the difference between java 8 ZonedDateTime and OffsetDateTime?
The easiest way to use it is as following:
currentISODate = new Date().parse("yyyy-MM-dd'T'HH:mm:ss", "2013-04-14T16:11:48.000");
where "yyyy-MM-dd'T'HH:mm:ss" is the format of the reading date
output: Sun Apr 14 16:11:48 EEST 2013
Notes: HH vs hh
- HH refers to 24h time format
- hh refers to 12h time format
public static void main(String[] args)
{
Date d = new Date();
SimpleDateFormat form = new SimpleDateFormat("dd-mm-yyyy hh:mm:ss");
System.out.println(form.format(d));
String str = form.format(d); // or if you want to save it in String str
System.out.println(str); // and print after that
}
Let's try this
public static void main(String args[]) {
Calendar cal = GregorianCalendar.getInstance();
Date today = cal.getTime();
DateFormat df7 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
try {
String str7 = df7.format(today);
System.out.println("String in yyyy-MM-dd format is: " + str7);
} catch (Exception ex) {
ex.printStackTrace();
}
}
Or a utility function
public String convertDateToString(Date date, String format) {
String dateStr = null;
DateFormat df = new SimpleDateFormat(format);
try {
dateStr = df.format(date);
} catch (Exception ex) {
ex.printStackTrace();
}
return dateStr;
}
From Convert Date to String in Java
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String date = "2010-05-30 22:15:52";
java.util.Date formatedDate = sdf.parse(date); // returns a String when it is parsed
System.out.println(sdf.format(formatedDate)); // the use of format function returns a String
Date date = new Date();
String strDate = String.format("%tY-%<tm-%<td %<tH:%<tM:%<tS", date);
One Line option
This option gets a easy one-line to write the actual date.
Please, note that this is using Calendar.class and SimpleDateFormat, and then it's not
logical to use it under Java8.
yourstringdate = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(Calendar.getInstance().getTime());

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