I am developing an application in JAVA swing, in that I wanted the date difference from current date like if today is 16/04/2013 then it should return 15/04/2013. I have tried the following code:
Calendar cal = new GregorianCalendar();
Calendar cal2 = new GregorianCalendar();
cal.roll(Calendar.DAY_OF_YEAR, -1);
//if within the first 30 days, need to roll the year as well
if(cal.after(cal2)){
cal.roll(Calendar.YEAR, -1);
}
System.out.println("Year " + cal.get(Calendar.YEAR));
System.out.println("Month " + cal.get(Calendar.MONTH));
System.out.println("Day " + cal.get(Calendar.DAY_OF_MONTH));
In this code I was expecting to get one day back date. But instead I am getting one month back date.
Ex. if today is 16/04/2013, the expected output is 15/04/2013, but I am getting 15/03/2013 ( one month one day back) as an output.
You dont need any manual manipulations, Calendar will do all necessary date arithmetic automatically, simply do this
Calendar cal = new GregorianCalendar();
cal.add(Calendar.DATE, -1);
Note that months in Calendar start from 0 so April is 3
That's a classic example why java.util.Date implementation sucks: Months numeration starts in zero:
0-> January
1-> February
2-> March
3-> April.
What you mean:
new Date(10,1,2013) //10th of January of 2013
What you get: 10th of February of 3983 (1970+2013)
Related
I want to get the last and the first week of a week for a given date.
e.g if the date is 12th October 2011 then I need the dates 10th October 2011 (as the starting date of the week) and 16th october 2011 (as the end date of the week)
Does anyone know how to get these 2 dates using the calender class (java.util.Calendar)
thanks a lot!
Some code how to do it with the Calendar object. I should also mention joda time library as it can help you many of Date/Calendar problems.
Code
public static void main(String[] args) {
// set the date
Calendar cal = Calendar.getInstance();
cal.set(2011, 10 - 1, 12);
// "calculate" the start date of the week
Calendar first = (Calendar) cal.clone();
first.add(Calendar.DAY_OF_WEEK,
first.getFirstDayOfWeek() - first.get(Calendar.DAY_OF_WEEK));
// and add six days to the end date
Calendar last = (Calendar) first.clone();
last.add(Calendar.DAY_OF_YEAR, 6);
// print the result
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
System.out.println(df.format(first.getTime()) + " -> " +
df.format(last.getTime()));
}
This solution works for any locale (first day of week could be Sunday or Monday).
Date date = new Date();
Calendar c = Calendar.getInstance();
c.setTime(date);
int dayOfWeek = c.get(Calendar.DAY_OF_WEEK) - c.getFirstDayOfWeek();
c.add(Calendar.DAY_OF_MONTH, -dayOfWeek);
Date weekStart = c.getTime();
// we do not need the same day a week after, that's why use 6, not 7
c.add(Calendar.DAY_OF_MONTH, 6);
Date weekEnd = c.getTime();
For example, today is Jan, 29 2014. For the locale with Sunday as a first day of week you will get:
start: 2014-01-26
end: 2014-02-01
For the locale with Monday as a first day the dates will be:
start: 2014-01-27
end: 2014-02-02
If you want all dates then
first.add(Calendar.DAY_OF_WEEK,first.getFirstDayOfWeek() - first.get(Calendar.DAY_OF_WEEK));
for (int i = 1; i <= 7; i++) {
System.out.println( i+" Day Of that Week is",""+first.getTime());
first.add(Calendar.DAY_OF_WEEK,1);
}
Here is the sample code
public static void main(String[] args) {
Calendar cal = Calendar.getInstance();
cal.set(2016, 2, 15);
{
Calendar startCal = Calendar.getInstance();
startCal.setTimeInMillis(cal.getTimeInMillis());
int dayOfWeek = startCal.get(Calendar.DAY_OF_WEEK);
startCal.set(Calendar.DAY_OF_MONTH,
(startCal.get(Calendar.DAY_OF_MONTH) - dayOfWeek) + 1);
System.out.println("end date : " + startCal.getTime());
}
{
Calendar endCal = Calendar.getInstance();
endCal.setTimeInMillis(cal.getTimeInMillis());
int dayOfWeek = endCal.get(Calendar.DAY_OF_WEEK);
endCal.set(Calendar.DAY_OF_MONTH, endCal.get(Calendar.DAY_OF_MONTH)
+ (7 - dayOfWeek));
System.out.println("start date : " + endCal.getTime());
}
}
which will print
start date : Sun Mar 13 20:30:30 IST 2016
end date : Sat Mar 19 20:30:30 IST 2016
I have found the formula in the accepted answer will only work in some cases. For example your week starts on Saturday and today is Sunday. To arrive at the first day of the week we walk back 1 day, but the formula cal.get(Calendar.DAY_OF_WEEK) - cal.getFirstDayOfWeek() will give the answer -6. The solution is to use a modulus so the formula wraps around so to speak.
int daysToMoveToStartOfWeek = (
7 +
cal.get(Calendar.DAY_OF_WEEK) -
cal.getFirstDayOfWeek()
)%7;
cal.add(Calendar.DAY_OF_WEEK, -1 * daysToMoveToStartOfWeek);
I want to get the date of the first monday of the current week and the first friday of the current week.
I tried it this way:
Calendar calendarFirstDay = Calendar.getInstance(Locale.GERMANY);
Calendar calendarLastDay = Calendar.getInstance(Locale.GERMANY);
Date now = new Date();
calendarFirstDay.setTime(now);
calendarLastDay.setTime(now);
calendarFirstDay.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
calendarLastDay.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY);
MyTextView.setText(calendarFirstDay.get(Calendar.DATE) + "." + calendarFirstDay.get(Calendar.MONTH) + "." + calendarFirstDay.get(Calendar.YEAR) + " - " + calendarLastDay.get(Calendar.DATE) + "." + calendarLastDay.get(Calendar.MONTH) + "." + calendarLastDay.get(Calendar.YEAR));
If I try this script today (Sunday, 26.1.2014), the output is the following:
20.0.2014 - 24.0.2014
Correct would be 20.1.2014 - 24.1.2014
Does somebody knows why my month is zero?
From the JavaDocs:
Field number for get and set indicating the month. This is a calendar-specific value. The first month of the year in the Gregorian and Julian calendars is JANUARY which is 0; the last depends on the number of months in a year.
Thus the first month (January) has a MONTH value of 0, and not 1 (as you'd expect).
There's a much better solution though: use a DateFormat or SimpleDateFormat to format dates as text. That way, you simply don't have to worry about this and let the DateFormat take care of it. For example:
DateFormat myFormat = new SimpleDateFormat("dd.MM.yyyy");
MyTextView.setText(
myFormat.format(calendarFirstDay.getTime()) + " - " +
myFormat.format(calendarLastDay.getTime())
);
As stated in
http://docs.oracle.com/javase/7/docs/api/java/util/Calendar.html#set(int,%20int,%20int)
if you use this method, January will be 0 and Decmember will be 11, so you should just add 1 to your month.
EDIT: You are using the get method but it's probably 0-based, too.
I want to get the last and the first week of a week for a given date.
e.g if the date is 12th October 2011 then I need the dates 10th October 2011 (as the starting date of the week) and 16th october 2011 (as the end date of the week)
Does anyone know how to get these 2 dates using the calender class (java.util.Calendar)
thanks a lot!
Some code how to do it with the Calendar object. I should also mention joda time library as it can help you many of Date/Calendar problems.
Code
public static void main(String[] args) {
// set the date
Calendar cal = Calendar.getInstance();
cal.set(2011, 10 - 1, 12);
// "calculate" the start date of the week
Calendar first = (Calendar) cal.clone();
first.add(Calendar.DAY_OF_WEEK,
first.getFirstDayOfWeek() - first.get(Calendar.DAY_OF_WEEK));
// and add six days to the end date
Calendar last = (Calendar) first.clone();
last.add(Calendar.DAY_OF_YEAR, 6);
// print the result
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
System.out.println(df.format(first.getTime()) + " -> " +
df.format(last.getTime()));
}
This solution works for any locale (first day of week could be Sunday or Monday).
Date date = new Date();
Calendar c = Calendar.getInstance();
c.setTime(date);
int dayOfWeek = c.get(Calendar.DAY_OF_WEEK) - c.getFirstDayOfWeek();
c.add(Calendar.DAY_OF_MONTH, -dayOfWeek);
Date weekStart = c.getTime();
// we do not need the same day a week after, that's why use 6, not 7
c.add(Calendar.DAY_OF_MONTH, 6);
Date weekEnd = c.getTime();
For example, today is Jan, 29 2014. For the locale with Sunday as a first day of week you will get:
start: 2014-01-26
end: 2014-02-01
For the locale with Monday as a first day the dates will be:
start: 2014-01-27
end: 2014-02-02
If you want all dates then
first.add(Calendar.DAY_OF_WEEK,first.getFirstDayOfWeek() - first.get(Calendar.DAY_OF_WEEK));
for (int i = 1; i <= 7; i++) {
System.out.println( i+" Day Of that Week is",""+first.getTime());
first.add(Calendar.DAY_OF_WEEK,1);
}
Here is the sample code
public static void main(String[] args) {
Calendar cal = Calendar.getInstance();
cal.set(2016, 2, 15);
{
Calendar startCal = Calendar.getInstance();
startCal.setTimeInMillis(cal.getTimeInMillis());
int dayOfWeek = startCal.get(Calendar.DAY_OF_WEEK);
startCal.set(Calendar.DAY_OF_MONTH,
(startCal.get(Calendar.DAY_OF_MONTH) - dayOfWeek) + 1);
System.out.println("end date : " + startCal.getTime());
}
{
Calendar endCal = Calendar.getInstance();
endCal.setTimeInMillis(cal.getTimeInMillis());
int dayOfWeek = endCal.get(Calendar.DAY_OF_WEEK);
endCal.set(Calendar.DAY_OF_MONTH, endCal.get(Calendar.DAY_OF_MONTH)
+ (7 - dayOfWeek));
System.out.println("start date : " + endCal.getTime());
}
}
which will print
start date : Sun Mar 13 20:30:30 IST 2016
end date : Sat Mar 19 20:30:30 IST 2016
I have found the formula in the accepted answer will only work in some cases. For example your week starts on Saturday and today is Sunday. To arrive at the first day of the week we walk back 1 day, but the formula cal.get(Calendar.DAY_OF_WEEK) - cal.getFirstDayOfWeek() will give the answer -6. The solution is to use a modulus so the formula wraps around so to speak.
int daysToMoveToStartOfWeek = (
7 +
cal.get(Calendar.DAY_OF_WEEK) -
cal.getFirstDayOfWeek()
)%7;
cal.add(Calendar.DAY_OF_WEEK, -1 * daysToMoveToStartOfWeek);
I have a bunch of dates formatted with the year and week, as follows:
2011-10
The week value is the week of the year(so 1-52). From this week value, I need to output something like the following:
Mar 7
Explicitly, I need the Month that the given week is in, and the date of the first Monday of that week. So in other words it is saying that the 10th week of the year is the week of March 7th.
I am using Groovy. What kind of date manipulation can I do to get this to work?
Here's a groovy solution:
use(groovy.time.TimeCategory) {
def (y, w) = "2011-10".tokenize("-")
w = ((w as int) + 1) as String
def d = Date.parse("yyyy-w", "$y-$w") + 1.day
println d.format("MMM dd")
}
Use a GregorianCalendar (or Joda, if you don't mind a dependency)
String date = "2011-10";
String[] parts = date.split("-");
Calendar cal = Calendar.getInstance();
cal.set(Calendar.YEAR, Integer.parseInt(parts[0]));
cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
cal.set(Calendar.WEEK_OF_YEAR, Integer.parseInt(parts[1])+1);
DateFormat df = new SimpleDateFormat("MMM d");
System.out.println(df.format(cal.getTime()) + " (" + cal.getTime() + ")");
EDIT: Added +1 to week, since calendar uses zero-based week numbers
Date date = new SimpleDateFormat("yyyy-w", Locale.UK).parse("2011-10");
System.out.println(new SimpleDateFormat("MMM d").format(date));
The first line returns first day of the 10th week in British Locale (March 7th). When Locale is not enforced, the results are dependent on default JVM Locale.
Formats are explained here.
You can use SimpleDateFormat, just like in java. See groovyconsole.appspot.com/script/439001
java.text.DateFormat df = new java.text.SimpleDateFormat('yyyy-w', new Locale('yourlocale'))
Date date = df.parse('2011-10')
To add a week, simply use Date date = df.parse('2011-10')+7
You don't need to set the Locale if your default Locale is using Monday as the first day of week.
I tried to do set date value to a PreparedStatement with default value but the value is sometimes returned as a JulianValue. For example (Assume spanBegin and spanEnd are null)
Calendar cal = new GregorianCalendar();
if (spanBegin == null) {
cal.set(0000, Calendar.JANUARY, 1);
spanBegin = cal.getTime();
}
if (spanEnd == null)
{
cal.set(9999, Calendar.DECEMBER, 31);
spanEnd = cal.getTime();
}
On line number 3, since the date January 1, 0000 is scoped by a Julian Calendar, the CDate becomes a Julian Calendar. However, the next Date even if it is in the year 9999, its CDate becomes a Julian Calendar still. I had　to create another instance of Gregorian Calendar to fix the issue.
Calendar cal = new GregorianCalendar();
if (spanBegin == null) {
cal.set(0000, Calendar.JANUARY, 1);
spanBegin = cal.getTime();
}
Calendar cal = new GregorianCalendar();
if (spanEnd == null)
{
cal.set(9999, Calendar.DECEMBER, 31);
spanEnd = cal.getTime();
}
The question is, is the this an expected behavior or a bug on the date object? Actually using GregorianCalendar.getInstance() shows that the cdate is sometimes set to JulianCalendar.
There was no Gregorian Calendar until 1582. The Julian calendar was in use all over Europe, until minor problems started to appear caused by the fact the solar year is not exactly 365.25 days, but a little less than that. In order to fix things, pope Gregory XIII ordered to change the calendar to what we know today - every year that divides by 100 is not a leap year, unless it divides by 400. In October 1582 there was the transition - the day after 4 Oct was 15 Oct. This means that until October 1582, the Gregorian and Julian Calendars are the same. You can read more about it here
This is why dates prior to Oct 1582 are converted to use the Julian system. According to the API If you actually need to represent an historical event (which seems not to by the case here) you can do it only from 1st march, 4AD
What version of Java are you using and on what OS? Do you really need to store dates in the years 0 and 9999, or are you just using these as "negative infinity" and "positive infinity" values? How exactly do you see that the calendar is a Julian calendar?
I tried this:
Calendar cal = Calendar.getInstance();
cal.set(0, Calendar.JANUARY, 1);
Date d1 = cal.getTime();
cal.set(9999, Calendar.DECEMBER, 31);
Date d2 = cal.getTime();
System.out.println(d1);
System.out.println(d2);
Output (on Windows XP, using Sun Java 1.6.0_16):
Thu Jan 01 09:53:56 CET 1 java.util.Date
Tue Dec 31 09:53:56 CET 9999 java.util.Date
It changes the year 0 to the year 1. Changing the code to use a second Calendar object for the second date:
Calendar cal = Calendar.getInstance();
cal.set(0, Calendar.JANUARY, 1);
Date d1 = cal.getTime();
Calendar cal2 = Calendar.getInstance();
cal2.set(9999, Calendar.DECEMBER, 31);
Date d2 = cal2.getTime();
System.out.println(d1);
System.out.println(d2);
This does not change anything to the output or the content of the two Date objects.
Note: Beware that integer literals that start with a 0, such as 0000 in your code, will be interpreted as octal numbers by the Java compiler. That doesn't matter in this case because the number is 0, but you should not prepend integer literals with zeroes if you don't mean them as octal numbers.
Thhere is no year 0 in Julian calendar. It goes from 1 BC to 1 AD.