Convert Date To Calendar Example

The Java language provides direct support for time-based objects. This article gives a few examples how this API can be used.

The java.util.Date and the java.util.Calendar classes provide access to storing and manipulating dates.

It is recommended to use Calendar if possible. Existing API may required that you convert from Date to Calendar and vice versa.
Firstly, I will show you how to work with Date and Calendar

Java Date Examples

Convert Date to String

SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
String date = sdf.format(new Date()); 
System.out.println(date); //21/03/2015

Convert String to Date

SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy hh:mm:ss");
String dateInString = "21-03-2015 22:20:56";
Date date = sdf.parse(dateInString);
System.out.println(date); //Sat Mar 21 10:20:56 SGT 2015

You can refer to SimpleDateFormat JavaDoc for detail date and time patterns.

Get current date time

SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Date date = new Date();
System.out.println(dateFormat.format(date)); //2015/03/21 20:23:39

Convert Calendar to Date

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

Java Calendar Examples

Get current date time

SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss"); 
Calendar calendar = new GregorianCalendar(2015,03,21);
System.out.println(sdf.format(calendar.getTime()));

Output

2015 Mar 21 00:00:00

Simple Calendar example

SimpleDateFormat sdf = new SimpleDateFormat("yyyy MMM dd HH:mm:ss"); 
Calendar calendar = new GregorianCalendar(2013,1,28,13,24,56);

int year       = calendar.get(Calendar.YEAR);
int month      = calendar.get(Calendar.MONTH); // Jan = 0, dec = 11
int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH); 
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);

System.out.println(sdf.format(calendar.getTime()));

System.out.println("year \t\t: " + year);
System.out.println("month \t\t: " + month);
System.out.println("dayOfMonth \t: " + dayOfMonth);
System.out.println("dayOfWeek \t: " + dayOfWeek);
System.out.println("weekOfYear \t: " + weekOfYear);
System.out.println("weekOfMonth \t: " + weekOfMonth);

System.out.println("hour \t\t: " + hour);
System.out.println("hourOfDay \t: " + hourOfDay);
System.out.println("minute \t\t: " + minute);
System.out.println("second \t\t: " + second);
System.out.println("millisecond \t: " + millisecond);

Output

2013 Feb 28 13:24:56
year   : 2013
month   : 1
dayOfMonth  : 28
dayOfWeek  : 5
weekOfYear  : 9
weekOfMonth     : 5
hour   : 1
hourOfDay  : 13
minute   : 24
second   : 56
millisecond     : 0

Set a date manually.

SimpleDateFormat sdf = new SimpleDateFormat("yyyy MMM dd HH:mm:ss"); 

Calendar calendar = new GregorianCalendar(2013,1,28,13,24,56); 
System.out.println("#1. " + sdf.format(calendar.getTime()));

//update a date
calendar.set(Calendar.YEAR, 2014);
calendar.set(Calendar.MONTH, 11);
calendar.set(Calendar.MINUTE, 33);

System.out.println("#2. " + sdf.format(calendar.getTime()));

Output

#1. 2013 Feb 28 13:24:56
#2. 2014 Dec 28 13:33:56

Add or subtract from a date.

SimpleDateFormat sdf = new SimpleDateFormat("yyyy MMM dd"); 

Calendar calendar = new GregorianCalendar(2013,10,28); 
System.out.println("Date : " + sdf.format(calendar.getTime()));

//add one month
calendar.add(Calendar.MONTH, 1);
System.out.println("Date : " + sdf.format(calendar.getTime()));

//subtract 10 days
calendar.add(Calendar.DAY_OF_MONTH, -10);
System.out.println("Date : " + sdf.format(calendar.getTime()));

Output

Date : 2013 Nov 28
Date : 2013 Dec 28
Date : 2013 Dec 18

Convert Date to Calendar.

SimpleDateFormat sdf = new SimpleDateFormat("dd-M-yyyy hh:mm:ss");
String dateInString = "22-01-2015 10:20:56";
Date date = sdf.parse(dateInString);

Calendar calendar = Calendar.getInstance();
calendar.setTime(date);

References

• mkyong.com
• vogella.com