Set time to 00:00:00

Question

I have a problem resetting hours in Java. For a given date I want to set the hours to 00:00:00.

This is my code :

/**
     * Resets milliseconds, seconds, minutes and hours from the provided date
     *
     * @param date
     * @return
     */
    public static Date trim(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.set(Calendar.MILLISECOND, 0);
        calendar.set(Calendar.SECOND, 0);
        calendar.set(Calendar.MINUTE, 0);
        calendar.set(Calendar.HOUR, 0);

        return calendar.getTime();
    }

The problem is that sometimes the time is 12:00:00 and sometimes it is 00:00:00 and when I query the database for an entity that was saved on 07.02.2013 00:00:00 and the actual entity time, that is stored, is 12:00:00 the query fails.

I know that 12:00:00 == 00:00:00!

I am using AppEngine. Is this an appengine bug, problem or some other issue? Or does it depend on something else?

Could this have something to do with different locales or does this happen from the same PC all the time? — LostBoy, Jul 23 '13 at 21:48
Lots of other solutions for cutting off time: http://stackoverflow.com/a/1908955/2646526 — heenenee, Feb 02 '16 at 01:23
FYI, the troublesome old date-time classes such as [`java.util.Date`](https://docs.oracle.com/javase/9/docs/api/java/util/Date.html), [`java.util.Calendar`](https://docs.oracle.com/javase/9/docs/api/java/util/Calendar.html), and `java.text.SimpleDateFormat` are now [legacy](https://en.wikipedia.org/wiki/Legacy_system), supplanted by the [java.time](https://docs.oracle.com/javase/9/docs/api/java/time/package-summary.html) classes built into Java 8 & Java 9. See [Tutorial by Oracle](https://docs.oracle.com/javase/tutorial/datetime/TOC.html). — Basil Bourque, Feb 01 '18 at 04:42
I used `calendar.set(Calendar.HOUR_OF_DAY, 0);`, for my purpose, it works well. — hariprasad, Jul 31 '19 at 13:02

rgettman · Accepted Answer · 2013-07-23T21:56:24.563

242

Use another constant instead of Calendar.HOUR, use Calendar.HOUR_OF_DAY.

calendar.set(Calendar.HOUR_OF_DAY, 0);

Calendar.HOUR uses 0-11 (for use with AM/PM), and Calendar.HOUR_OF_DAY uses 0-23.

To quote the Javadocs:

public static final int HOUR

Field number for get and set indicating the hour of the morning or afternoon. HOUR is used for the 12-hour clock (0 - 11). Noon and midnight are represented by 0, not by 12. E.g., at 10:04:15.250 PM the HOUR is 10.

and

public static final int HOUR_OF_DAY

Field number for get and set indicating the hour of the day. HOUR_OF_DAY is used for the 24-hour clock. E.g., at 10:04:15.250 PM the HOUR_OF_DAY is 22.

Testing ("now" is currently c. 14:55 on July 23, 2013 Pacific Daylight Time):

public class Main
{
   static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    public static void main(String[] args)
    {
        Calendar now = Calendar.getInstance();
        now.set(Calendar.HOUR, 0);
        now.set(Calendar.MINUTE, 0);
        now.set(Calendar.SECOND, 0);
        System.out.println(sdf.format(now.getTime()));
        now.set(Calendar.HOUR_OF_DAY, 0);
        System.out.println(sdf.format(now.getTime()));
    }
}

Output:

$ javac Main.java
$ java Main
2013-07-23 12:00:00
2013-07-23 00:00:00

edited Jul 23 '13 at 21:56

answered Jul 23 '13 at 21:45

rgettman

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@JarrodRoberson But using `Calendar.HOUR` wouldn't set PM to AM, leaving it as 12:00 noon. – rgettman Jul 23 '13 at 21:48
Can you please help me in constructing a LocalDate with hours, minute and second? I know one option is to follow DateTime. – Woody Jul 23 '15 at 10:05
16

Whoever created the field HOUR and HOUR_OF_DAY should have been flogged and put on rations. – Johann Sep 08 '15 at 14:19
2

@AndroidDev whoever invented am/pm deserves the same... This also goes for non-metric standards – Dediqated Sep 09 '16 at 15:09
1

FYI, the troublesome old date-time classes such as [`java.util.Date`](https://docs.oracle.com/javase/9/docs/api/java/util/Date.html), [`java.util.Calendar`](https://docs.oracle.com/javase/9/docs/api/java/util/Calendar.html), and `java.text.SimpleDateFormat` are now [legacy](https://en.wikipedia.org/wiki/Legacy_system), supplanted by the [java.time](https://docs.oracle.com/javase/9/docs/api/java/time/package-summary.html) classes built into Java 8 & Java 9. See [Tutorial by Oracle](https://docs.oracle.com/javase/tutorial/datetime/TOC.html). – Basil Bourque Feb 01 '18 at 04:42
2

All is correct, but there should be millis also: now.set(Calendar.MILLISECOND, 0); – Sergey Chepurnov Jan 29 '19 at 03:31
You can set Minutes and Seconds too . Say for example : calender.set(Calendar.MINUTE, 59); calender.set(Calendar.SECOND, 46); – Pratik Roy Jun 23 '21 at 05:26

Przemek · Answer 2 · 2016-01-13T12:43:24.047

41

java.time

Using the java.time framework built into Java 8 and later. See Tutorial.

import java.time.LocalTime;
import java.time.LocalDateTime;

LocalDateTime now = LocalDateTime.now(); # 2015-11-19T19:42:19.224
# start of a day
now.with(LocalTime.MIN); # 2015-11-19T00:00
now.with(LocalTime.MIDNIGHT); # 2015-11-19T00:00

If you do not need time-of-day (hour, minute, second etc. parts) consider using LocalDate class.

LocalDate.now(); # 2015-11-19

edited Jan 13 '16 at 12:43

answered Nov 19 '15 at 18:54

Przemek

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This should be the new accepted answer since Java 1.8 has been released since this question was first asked. – matt forsythe Feb 01 '18 at 18:00
`LocalDateTime` is exactly the **wrong class** to use for this. It cannot represent a moment as it lacks any concept of time zone or offset-from-UTC. Calling `LocalDateTime.now` almost never makes sense. Use `ZonedDateTime` instead. Otherwise you are ignoring crucial time zone issues. For one thing, some dates in some zones do *not* start at 00:00! – Basil Bourque May 26 '19 at 20:28

score 15 · Answer 3 · answered Jul 23 '13 at 21:50

Here are couple of utility functions I use to do just this.

/**
 * sets all the time related fields to ZERO!
 *
 * @param date
 *
 * @return Date with hours, minutes, seconds and ms set to ZERO!
 */
public static Date zeroTime( final Date date )
{
    return DateTimeUtil.setTime( date, 0, 0, 0, 0 );
}

/**
 * Set the time of the given Date
 *
 * @param date
 * @param hourOfDay
 * @param minute
 * @param second
 * @param ms
 *
 * @return new instance of java.util.Date with the time set
 */
public static Date setTime( final Date date, final int hourOfDay, final int minute, final int second, final int ms )
{
    final GregorianCalendar gc = new GregorianCalendar();
    gc.setTime( date );
    gc.set( Calendar.HOUR_OF_DAY, hourOfDay );
    gc.set( Calendar.MINUTE, minute );
    gc.set( Calendar.SECOND, second );
    gc.set( Calendar.MILLISECOND, ms );
    return gc.getTime();
}

score 14 · Answer 4 · answered Jul 26 '17 at 11:47

14

One more JAVA 8 way:

LocalDateTime localDateTime = LocalDateTime.now().truncatedTo(ChronoUnit.HOURS);

But it's a lot more useful to edit the date that already exists.

answered Jul 26 '17 at 11:47

thorinkor

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`LocalDateTime` cannot represent a moment, as it lacks any concept of time zone or offset-from-UTC. Calling `LocalDateTime.now` almost never makes sense. You should be using `ZonedDateTime` instead. – Basil Bourque May 26 '19 at 20:10

score 6 · Answer 5 · answered Jun 29 '21 at 07:15

See the below code:

    String datePattern24Hrs = "yyyy-MM-dd HH:mm:ss";
    String datePattern12Hrs = "yyyy-MM-dd hh:mm:ss";

    SimpleDateFormat simpleDateFormat24Hrs = new SimpleDateFormat(datePattern24Hrs);
    SimpleDateFormat simpleDateFormat12Hrs = new SimpleDateFormat(datePattern12Hrs);

    Date dateNow = new Date();
    Calendar calendar = Calendar.getInstance();
    calendar.setTime(dateNow);
    calendar.set(Calendar.HOUR_OF_DAY, 0);
    calendar.set(Calendar.MINUTE, 0);
    calendar.set(Calendar.SECOND, 0);
    calendar.set(Calendar.MILLISECOND, 0);
    Date dateTime = calendar.getTime();

    String dateTimeIn24Hrs = simpleDateFormat24Hrs.format(dateTime);
    String dateTimeIn12Hrs = simpleDateFormat12Hrs.format(dateTime);

    System.out.println("DateTime in 24Hrs: ".concat(dateTimeIn24Hrs));
    System.out.println("DateTime in 12Hrs: ".concat(dateTimeIn12Hrs));

The expected output is as below:

DateTime in 24Hrs: 2021-06-29 00:00:00
DateTime in 12Hrs: 2021-06-29 12:00:00

I hope it helps with the answer you are looking for.

score 3 · Answer 6 · answered Oct 27 '17 at 15:51

You would better to primarily set time zone to the DateFormat component like this:

DateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
dateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));

Then you can get "00:00:00" time by passing 0 milliseconds to formatter:

String time = dateFormat.format(0);

or you can create Date object:

Date date = new Date(0); // also pass milliseconds
String time = dateFormat.foramt(date);

or you be able to have more possibilities using Calendar component but you should also set timezone as GMT to calendar instance:

Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"), Locale.US);
calendar.set(Calendar.HOUR_OF_DAY, 5);
calendar.set(Calendar.MINUTE, 37);
calendar.set(Calendar.SECOND, 27);

dateFormat.format(calendar.getTime());

Chao Jiang · Answer 7 · 2019-01-14T05:55:33.210

As Java8 add new Date functions, we can do this easily.


    // If you have instant, then:
    Instant instant1 = Instant.now();
    Instant day1 = instant1.truncatedTo(ChronoUnit.DAYS);
    System.out.println(day1); //2019-01-14T00:00:00Z

    // If you have Date, then:
    Date date = new Date();
    Instant instant2 = date.toInstant();
    Instant day2 = instant2.truncatedTo(ChronoUnit.DAYS);
    System.out.println(day2); //2019-01-14T00:00:00Z

    // If you have LocalDateTime, then:
    LocalDateTime dateTime = LocalDateTime.now();
    LocalDateTime day3 = dateTime.truncatedTo(ChronoUnit.DAYS);
    System.out.println(day3); //2019-01-14T00:00
    String format = day3.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME);
    System.out.println(format);//2019-01-14T00:00:00

`LocalDateTime` cannot represent a moment, as it lacks any concept of time zone or offset-from-UTC. Calling `LocalDateTime.now` almost never makes sense. You should be using `ZonedDateTime` instead. — Basil Bourque, May 26 '19 at 20:08

score 3 · Answer 8 · answered May 26 '19 at 20:22

tl;dr

myJavaUtilDate                                 // The terrible `java.util.Date` class is now legacy. Use *java.time* instead.
.toInstant()                                   // Convert this moment in UTC from the legacy class `Date` to the modern class `Instant`.
.atZone( ZoneId.of( "Africa/Tunis" ) )         // Adjust from UTC to the wall-clock time used by the people of a particular region (a time zone).
.toLocalDate()                                 // Extract the date-only portion.
.atStartOfDay( ZoneId.of( "Africa/Tunis" ) )   // Determine the first moment of that date in that zone. The day does *not* always start at 00:00:00.

java.time

You are using terrible old date-time classes that were supplanted years ago by the modern java.time classes defined in JSR 310.

`Date` ➙ `Instant`

A java.util.Date represent a moment in UTC. Its replacement is Instant. Call the new conversion methods added to the old classes.

Instant instant = myJavaUtilDate.toInstant() ;

Time zone

Specify the time zone in which you want your new time-of-day to make sense.

Specify a proper time zone name in the format of Continent/Region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 2-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!).

ZoneId z = ZoneId.of( "America/Montreal" ) ;

`ZonedDateTime`

Apply the ZoneId to the Instant to get a ZonedDateTime. Same moment, same point on the timeline, but different wall-clock time.

ZonedDateTime zdt = instant.atZone( z ) ;

Changing time-of-day

You asked to change the time-of-day. Apply a LocalTime to change all the time-of-day parts: hour, minute, second, fractional second. A new ZonedDateTime is instantiated, with values based on the original. The java.time classes use this immutable objects pattern to provide thread-safety.

LocalTime lt = LocalTime.of( 15 , 30 ) ;  // 3:30 PM.
ZonedDateTime zdtAtThreeThirty = zdt.with( lt ) ;

First moment of day

But you asked specifically for 00:00. So apparently you want the first moment of the day. Beware: some days in some zones do not start at 00:00:00. They may start at another time such as 01:00:00 because of anomalies such as Daylight Saving Time (DST).

Let java.time determine the first moment. Extract the date-only portion. Then pass the time zone to get first moment.

LocalDate ld = zdt.toLocalDate() ;
ZonedDateTime zdtFirstMomentOfDay = ld.atStartOfDay( z ) ;

Adjust to UTC

If you need to go back to UTC, extract an Instant.

Instant instant = zdtFirstMomentOfDay.toInstant() ;

`Instant` ➙ `Date`

If you need a java.util.Date to interoperate with old code not yet updated to java.time, convert.

java.util.Date d = java.util.Date.from( instant ) ;

score 2 · Answer 9 · answered Nov 30 '20 at 11:48

Another simple way,

final Calendar today = Calendar.getInstance();
        today.setTime(new Date());
        today.clear(Calendar.HOUR_OF_DAY);
        today.clear(Calendar.HOUR);
        today.clear(Calendar.MINUTE);
        today.clear(Calendar.SECOND);
        today.clear(Calendar.MILLISECOND);

score 2 · Answer 10 · answered May 07 '21 at 20:15

2

Before Java 8:

Calendar calendar = Calendar.getInstance();
calendar.setTime(new Date());
calendar.set(Calendar.HOUR, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);

After Java 8:

LocalDateTime.now().with(LocalTime.of(0, 0, 0))

answered May 07 '21 at 20:15

Jadson Santos

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score 1 · Answer 11 · edited Feb 28 '17 at 15:34

1

Doing this could be easier (In Java 8)

LocalTime.ofNanoOfDay(0)

edited Feb 28 '17 at 15:34

Adelin

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answered Feb 28 '17 at 13:40

meszias

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Thank you, I worked with other stuff last 2 years, and Java 6/7 before it. I've back to Java now (after worked with few things on Groovy) and liking Java 8 differences. – meszias Feb 28 '17 at 19:30

MMascarin · Answer 12 · 2016-10-06T08:48:10.930

0

Another way to do this would be to use a DateFormat without any seconds:

public static Date trim(Date date) {
    DateFormat format = new SimpleDateFormat("dd.MM.yyyy");
    Date trimmed = null;
    try {
        trimmed = format.parse(format.format(date));
    } catch (ParseException e) {} // will never happen
    return trimmed;
}

edited Oct 06 '16 at 08:48

answered Aug 20 '15 at 09:46

MMascarin

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score 0 · Answer 13 · answered Mar 31 '18 at 00:20

0

You can either do this with the following:

Calendar cal = Calendar.getInstance();
cal.set(year, month, dayOfMonth, 0, 0, 0);
Date date = cal.getTime();

answered Mar 31 '18 at 00:20

SagarScript

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score 0 · Answer 14 · answered Oct 29 '18 at 03:46

If you need format 00:00:00 in string, you should use SimpleDateFormat as below. Using "H "instead "h".

Date today = new Date();
SimpleDateFormat ft = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss"); 
//not SimpleDateFormat("dd-MM-yyyy hh:mm:ss")
Calendar calendarDM = Calendar.getInstance();
calendarDM.setTime(today);
calendarDM.set(Calendar.HOUR, 0);
calendarDM.set(Calendar.MINUTE, 0);
calendarDM.set(Calendar.SECOND, 0);
System.out.println("Current Date: " + ft.format(calendarDM.getTime()));

//Result is: Current Date: 29-10-2018 00:00:00

Set time to 00:00:00

14 Answers14

java.time

tl;dr

java.time

`Date` ➙ `Instant`

Time zone

`ZonedDateTime`

Changing time-of-day

First moment of day

Adjust to UTC

`Instant` ➙ `Date`

Linked

Related

Set time to 00:00:00

14 Answers14

java.time

tl;dr

java.time

Date ➙ Instant

Time zone

ZonedDateTime

Changing time-of-day

First moment of day

Adjust to UTC

Instant ➙ Date

Linked

Related

`Date` ➙ `Instant`

`ZonedDateTime`

`Instant` ➙ `Date`