Java create date year month day

Guide to java.util.Date Class

Learn to create new date, get current date, parse date to string or format Date object using java.util.Date class. These usecases are frequently required, and having them in one place will help in saving time for many of us.

It is worth noting that there is no timezone information associated with Date instance. A Date instance represents the time spent since Epach in milliseconds. If we print the date instance, it always prints the default or local timezone of the machine. So the timezone information printed in Date.toString() method should not misguide you.

1. Formatting a Date to String

Java program of formatting Date to string using SimpleDateFormat.format() . Please note that SimpleDateFormat is not a thread-safe class, so we should not share its instance with multiple threads.

SimpleDateFormat sdf = new SimpleDateFormat("dd/M/yyyy"); String date = sdf.format(new Date());

Refer SimpleDateFormat JavaDoc for detailed date and time patterns. Below is a list of the most common pattern letters you can use.

y = year (yy or yyyy) M = month (MM) d = day in month (dd) h = hour (0-12) (hh) H = hour (0-23) (HH) m = minute in hour (mm) s = seconds (ss) S = milliseconds (SSS) z = time zone text (e.g. Pacific Standard Time. ) Z = time zone, time offset (e.g. -0800)

Pattern	Example
yyyy-MM-dd (ISO)	“2018-07-14”
dd-MMM-yyyy	“14-Jul-2018”
dd/MM/yyyy	“14/07/2018”
E, MMM dd yyyy	“Sat, Jul 14 2018”
h:mm a	“12:08 PM”
EEEE, MMM dd, yyyy HH:mm:ss a	“Saturday, Jul 14, 2018 14:31:06 PM”
yyyy-MM-dd’T’HH:mm:ssZ	“2018-07-14T14:31:30+0530”
hh ‘o»clock’ a, zzzz	“12 o’clock PM, Pacific Daylight Time”
K:mm a, z	“0:08 PM, PDT”

2. Parsing a String to Date

Java program of parsing a string to Date instance using SimpleDateFormat.parse() method.

SimpleDateFormat sdf = new SimpleDateFormat("dd-M-yyyy hh:mm:ss"); String dateInString = "15-10-2015 10:20:56"; Date date = sdf.parse(dateInString);

3. Getting Current Date and Time

java.util.Date class represents the date and time elapsed since the epoch. Given below are the Java programs for getting the current date and time and printing in a given format.

SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss"); Date date = new Date(); System.out.println(dateFormat.format(date)); 

For reference, since Java 8, we can use LocalDate , LocalTime and LocalDateTime classes.

LocalDate today = LocalDate.now(); System.out.println("Today's Local date : " + today); LocalTime time = LocalTime.now(); System.out.println("local time now : " + time);

4. Convert between Date and Calendar

4.1. Converting Calendar to Date

Calendar calendar = Calendar.getInstance(); Date date = calendar.getTime();

4.2. Converting Date to Calendar

SimpleDateFormat sdf = new SimpleDateFormat("dd-M-yyyy hh:mm:ss"); String dateInString = "27-04-2016 10:22:56"; Date date = sdf.parse(dateInString); Calendar calendar = Calendar.getInstance(); calendar.setTime(date); 

We can compare two two date instances using its compareTo() method. It returns an integer value representing given date is before or after another date.

The comparison date1.CompareTo(date2) will return:

• a value 0 if date2 is equal to date1;
• a value less than 0 if date1 is before date2;
• a value greater than 0 if date1 is after date2.

Date date1 = new Date(); Date date2 = new Date(); int comparison = date1.compareTo(date2);

6. Extracting Days, Months and Years

Java program to get date parts such as year, month, etc separately.

The methods to get the year, month, day of the month, hour, etc. are deprecated. If you need to get or set the year, month, day of the month, etc. use a java.util.Calendar instead.

Calendar calendar = Calendar.getInstance(); calendar.setTime(new Date()); int year = calendar.get(Calendar.YEAR); int month = calendar.get(Calendar.MONTH); int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH); // Jan = 0, not 1 int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK); int weekOfYear = calendar.get(Calendar.WEEK_OF_YEAR); int weekOfMonth= calendar.get(Calendar.WEEK_OF_MONTH); int hour = calendar.get(Calendar.HOUR); // 12 hour clock int hourOfDay = calendar.get(Calendar.HOUR_OF_DAY); // 24 hour clock int minute = calendar.get(Calendar.MINUTE); int second = calendar.get(Calendar.SECOND); int millisecond= calendar.get(Calendar.MILLISECOND);

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Class Date

Prior to JDK 1.1, the class Date had two additional functions. It allowed the interpretation of dates as year, month, day, hour, minute, and second values. It also allowed the formatting and parsing of date strings. Unfortunately, the API for these functions was not amenable to internationalization. As of JDK 1.1, the Calendar class should be used to convert between dates and time fields and the DateFormat class should be used to format and parse date strings. The corresponding methods in Date are deprecated.

Although the Date class is intended to reflect coordinated universal time (UTC), it may not do so exactly, depending on the host environment of the Java Virtual Machine. Nearly all modern operating systems assume that 1 day = 24 × 60 × 60 = 86400 seconds in all cases. In UTC, however, about once every year or two there is an extra second, called a «leap second.» The leap second is always added as the last second of the day, and always on December 31 or June 30. For example, the last minute of the year 1995 was 61 seconds long, thanks to an added leap second. Most computer clocks are not accurate enough to be able to reflect the leap-second distinction.

Some computer standards are defined in terms of Greenwich mean time (GMT), which is equivalent to universal time (UT). GMT is the «civil» name for the standard; UT is the «scientific» name for the same standard. The distinction between UTC and UT is that UTC is based on an atomic clock and UT is based on astronomical observations, which for all practical purposes is an invisibly fine hair to split. Because the earth’s rotation is not uniform (it slows down and speeds up in complicated ways), UT does not always flow uniformly. Leap seconds are introduced as needed into UTC so as to keep UTC within 0.9 seconds of UT1, which is a version of UT with certain corrections applied. There are other time and date systems as well; for example, the time scale used by the satellite-based global positioning system (GPS) is synchronized to UTC but is not adjusted for leap seconds. An interesting source of further information is the United States Naval Observatory (USNO):

and the material regarding «Systems of Time» at:

which has descriptions of various different time systems including UT, UT1, and UTC.

• A year y is represented by the integer y — 1900 .
• A month is represented by an integer from 0 to 11; 0 is January, 1 is February, and so forth; thus 11 is December.
• A date (day of month) is represented by an integer from 1 to 31 in the usual manner.
• An hour is represented by an integer from 0 to 23. Thus, the hour from midnight to 1 a.m. is hour 0, and the hour from noon to 1 p.m. is hour 12.
• A minute is represented by an integer from 0 to 59 in the usual manner.
• A second is represented by an integer from 0 to 61; the values 60 and 61 occur only for leap seconds and even then only in Java implementations that actually track leap seconds correctly. Because of the manner in which leap seconds are currently introduced, it is extremely unlikely that two leap seconds will occur in the same minute, but this specification follows the date and time conventions for ISO C.

In all cases, arguments given to methods for these purposes need not fall within the indicated ranges; for example, a date may be specified as January 32 and is interpreted as meaning February 1.

Constructor Summary

Allocates a Date object and initializes it so that it represents the time at which it was allocated, measured to the nearest millisecond.

As of JDK version 1.1, replaced by Calendar.set(year + 1900, month, date) or GregorianCalendar(year + 1900, month, date) .

As of JDK version 1.1, replaced by Calendar.set(year + 1900, month, date, hrs, min) or GregorianCalendar(year + 1900, month, date, hrs, min) .

As of JDK version 1.1, replaced by Calendar.set(year + 1900, month, date, hrs, min, sec) or GregorianCalendar(year + 1900, month, date, hrs, min, sec) .

Allocates a Date object and initializes it to represent the specified number of milliseconds since the standard base time known as «the epoch», namely January 1, 1970, 00:00:00 GMT.

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How to get a Date from year, month and day in Java?

The of() method of the java.time.LocalDate class accepts the values of the year, month, and day of month as parameters, creates and returns an object of the LocalDate.

Example

import java.time.LocalDate; public class Test < public static void main(String[] args) < LocalDate date = LocalDate.of(2014, 9, 11); System.out.println("Date Value: "+date); >>

Output

Using the GregorianCalendar class

One of the constructors of the java.util.GregorianCalendar class accepts the values of year, month and day of month as values and creates a Calendar object representing it.

Example

import java.util.*; class Test < public static void main(String args[])< //Creating a calendar object Calendar cal = new GregorianCalendar(2020, 07, 18); int day = cal.get(Calendar.DAY_OF_MONTH); int month = cal.get(Calendar.MONTH); int year = cal.get(Calendar.YEAR); System.out.println("Day: " + day); System.out.println("Month: " + month); System.out.println("Year: " + year); >>

Output

Using the SimpleDateFormat object

One of the constructors of this class accepts a String value representing the desired date format and creates SimpleDateFormat object. To parse/convert a string as a Date object −

• Instantiate this class by passing desired format string.
• Parse the date string using the parse() method.

Example

import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date; public class Sample < public static void main(String args[]) throws ParseException < String date_string = "2007-25-06"; //Instantiating the SimpleDateFormat class SimpleDateFormat formatter = new SimpleDateFormat("yyyy-dd-MM"); //Parsing the given String to Date object Date date = formatter.parse(date_string); System.out.println("Date value: "+date); >>

Output

Date value: Mon Jun 25 00:00:00 IST 2007

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