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Calendar offset issue

I need to get the month and day of today's date and offset dates. This is how I do it:
Calendar calendar = Calendar.getInstance();
calendar.add(Calendar.DAY_OF_WEEK, 0);
Date today = calendar.getTime();
System.out.println(today);
Output:
Wed Aug 27 15:07:35 CEST 2014
Two things, I need the month and the day to be numeric, like 8/27. I understand how to do that with today's date like so:
int day = calendar.get(Calendar.DAY_OF_MONTH);
int month = calendar.get(Calendar.MONTH);
String a = String.valueOf(day);
String b = String.valueOf(month);
System.out.println(b +"/" + a);
My issue is that I might need to add an offset to that date, if I want tomorrows date for example. Is there a way to do that because converting Wed Aug 27.... to 8/27 would just be a pain. Thanks

Use simple date format:
Something like:
Calendar calendar = Calendar.getInstance();
calendar.add(Calendar.DAY_OF_WEEK, 1);
Date today = calendar.getTime();
SimpleDateFormat sdf = new SimpleDateFormat("dd.MM.yyyy HH:mm:ss");
System.out.println(sdf.format(today));

DateFormat formatter = new SimpleDateFormat("MM/dd");
Calendar cal = Calendar.getInstance();
String calAsString = formatter.format(cal.getTime());
System.out.println(calAsString);
// Now for tomorrow's date:
int offset = 1;
cal.add(Calendar.DATE, offset);
calAsString = formatter.format(cal.getTime());
System.out.println(calAsString);

Use the Calendar to add a value to the day:
Calendar calendar = Calendar.getInstance();
calendar.add(Calendar.DAY_OF_MONTH,1)

How to reduce one month from current date and stored in date variable using java?

How to reduce one month from current date and want to sore in java.util.Date variable
im using this code but it's shows error in 2nd line
java.util.Date da = new Date();
da.add(Calendar.MONTH, -1); //error
How to store this date in java.util.Date variable?

Use Calendar:
Calendar cal = Calendar.getInstance();
cal.add(Calendar.MONTH, -1);
Date result = cal.getTime();

Starting from Java 8, the suggested way is to use the Date-Time API rather than Calendar.
If you want a Date object to be returned:
Date date = Date.from(ZonedDateTime.now().minusMonths(1).toInstant());
If you don't need exactly a Date object, you can use the classes directly, provided by the package, even to get dates in other time-zones:
ZonedDateTime dateInUTC = ZonedDateTime.now(ZoneId.of("Pacific/Auckland")).minusMonths(1);

Calendar calNow = Calendar.getInstance()
// adding -1 month
calNow.add(Calendar.MONTH, -1);
// fetching updated time
Date dateBeforeAMonth = calNow.getTime();

you can use Calendar
java.util.Date da = new Date();
Calendar cal = Calendar.getInstance();
cal.setTime(da);
cal.add(Calendar.MONTH, -1);
da = cal.getTime();

Using new java.time package in Java8 and Java9
import java.time.LocalDate;
LocalDate mydate = LocalDate.now(); // Or whatever you want
mydate = mydate.minusMonths(1);
The advantage to using this method is that you avoid all the issues about varying month lengths and have more flexibility in adjusting dates and ranges. The Local part also is Timezone smart so it's easy to convert between them.
As an aside, using java.time you can also get the day of the week, day of the month, all days up to the last of the month, all days up to a certain day of the week, etc.
mydate.plusMonths(1);
mydate.with(TemporalAdjusters.next(DayOfWeek.SUNDAY)).getDayOfMonth();
mydate.with(TemporalAdjusters.lastDayOfMonth());

Using JodaTime :
Date date = new DateTime().minusMonths(1).toDate();
JodaTime provides a convenient API for date manipulation.
Note that similar Date API will be introduced in JDK8 with the JSR310.

You can also use the DateUtils from apache common. The library also supports adding Hour, Minute, etc.
Date date = DateUtils.addMonths(new Date(), -1)

raduce 1 month of JDF
Date dateTo = new SimpleDateFormat("yyyy/MM/dd").parse(jdfMeTo.getJulianDate());
Calendar cal = Calendar.getInstance();
cal.setTime(dateTo);
cal.add(Calendar.MONTH, -1);
Date dateOf = cal.getTime();
Log.i("dateOf", dateOf.getTime() + "");
jdfMeOf.setJulianDate(cal.get(Calendar.DAY_OF_YEAR), cal.get(Calendar.DAY_OF_MONTH),
cal.get(Calendar.DAY_OF_WEEK_IN_MONTH));

last day of month calculation

I am having issues with the calculation of when the next Last Day of the Month is for a notification which is scheduled to be sent.
Here is my code:
RecurrenceFrequency recurrenceFrequency = notification.getRecurrenceFrequency();
Calendar nextNotifTime = Calendar.getInstance();
This is the line causing issues I believe:
nextNotifTime.add(recurrenceFrequency.getRecurrencePeriod(),
recurrenceFrequency.getRecurrenceOffset());
How can I use the Calendar to properly set the last day of the next month for the notification?

Calendar.getInstance().getActualMaximum(Calendar.DAY_OF_MONTH);
This returns actual maximum for current month. For example it is February of leap year now, so it returns 29 as int.

java.time.temporal.TemporalAdjusters.lastDayOfMonth()
Using the java.time library built into Java 8, you can use the TemporalAdjuster interface. We find an implementation ready for use in the TemporalAdjusters utility class: lastDayOfMonth.
import java.time.LocalDate;
import java.time.temporal.TemporalAdjusters;
LocalDate now = LocalDate.now(); //2015-11-23
LocalDate lastDay = now.with(TemporalAdjusters.lastDayOfMonth()); //2015-11-30
If you need to add time information, you may use any available LocalDate to LocalDateTime conversion like
lastDay.atStartOfDay(); //2015-11-30T00:00

And to get last day as Date object:
Calendar cal = Calendar.getInstance();
cal.set(Calendar.DATE, cal.getActualMaximum(Calendar.DATE));
Date lastDayOfMonth = cal.getTime();

You can set the calendar to the first of next month and then subtract a day.
Calendar nextNotifTime = Calendar.getInstance();
nextNotifTime.add(Calendar.MONTH, 1);
nextNotifTime.set(Calendar.DATE, 1);
nextNotifTime.add(Calendar.DATE, -1);
After running this code nextNotifTime will be set to the last day of the current month. Keep in mind if today is the last day of the month the net effect of this code is that the Calendar object remains unchanged.

Following will always give proper results:
Calendar cal = Calendar.getInstance();
cal.set(Calendar.MONTH, ANY_MONTH);
cal.set(Calendar.YEAR, ANY_YEAR);
cal.set(Calendar.DAY_OF_MONTH, 1);// This is necessary to get proper results
cal.set(Calendar.DATE, cal.getActualMaximum(Calendar.DATE));
cal.getTime();

You can also use YearMonth.
Like:
YearMonth.of(2019,7).atEndOfMonth()
YearMonth.of(2019,7).atDay(1)
See
https://docs.oracle.com/javase/8/docs/api/java/time/YearMonth.html#atEndOfMonth--

Using the latest java.time library here is the best solution:
LocalDate date = LocalDate.now();
LocalDate endOfMonth = date.with(TemporalAdjusters.lastDayOfMonth());
Alternatively, you can do:
LocalDate endOfMonth = date.withDayOfMonth(date.lengthOfMonth());

Look at the getActualMaximum(int field) method of the Calendar object.
If you set your Calendar object to be in the month for which you are seeking the last date, then getActualMaximum(Calendar.DAY_OF_MONTH) will give you the last day.

SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
Date date = sdf.parse("11/02/2016");
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
System.out.println("First Day Of Month : " + calendar.getActualMinimum(Calendar.DAY_OF_MONTH));
System.out.println("Last Day of Month : " + calendar.getActualMaximum(Calendar.DAY_OF_MONTH));

Kotlin date extension implementation using java.util.Calendar
fun Date.toEndOfMonth(): Date {
return Calendar.getInstance().apply {
time = this#toEndOfMonth
}.toEndOfMonth().time
}
fun Calendar.toEndOfMonth(): Calendar {
set(Calendar.DAY_OF_MONTH, getActualMaximum(Calendar.DAY_OF_MONTH))
return this
}
You can call toEndOfMonth function on each Date object like Date().toEndOfMonth()

Date text box should be always 1st date current month.?

I want a javascript or java program should always give date 1st of current month.
Is there any tech?

You can use Calendar for Java
Date date = new Date(System.currentTimeMillis());
cal = Calendar.getInstance();
cal.setTime(date);
cal.set(Calendar.DAY_OF_MONTH, 1);
Now you do what every you want to do with this Calendar object like to get the Day of the Week (Sat, Sun, .... )
int weekday = cal.get(Calendar.DAY_OF_WEEK);
And for JavaScript you can use:
var theFirst = new Date();
theFirst.setDate(1);
setDate sets the day of the month for the Date object (from 1 to 31). Then you can do whatever you want with theFirst, like get the day of the week.

Calendar ans = Calendar.getInstance();
ans.set(ans.get(Calendar.YEAR),
ans.get(Calendar.MONTH),
1,
0,
0,
0
);
System.out.println(ans.getTime());

Java ResultSet how to getTimeStamp in UTC

The database has data in UTC and when I try to get data
java.util.Calendar cal = Calendar.getInstance();
cal.setTimeZone(TimeZone.getTimeZone("UTC"));
java.sql.Timestamp ts = resultSet.getTimestamp(PUBLISH_TIME);
cal.setTime(ts);
Is there anything wrong with this?

java.util.Calendar cal = Calendar.getInstance();
cal.setTimeZone(TimeZone.getTimeZone("UTC"));
java.sql.Timestamp ts = resultSet.getTimestamp(PUBLISH_TIME, cal);
This should do the trick!

Your DateFormat instance is most likely displaying the value in local time. When displaying your value, give this a try:
java.util.Calendar cal = Calendar.getInstance();
cal.setTimeZone(TimeZone.getTimeZone("UTC"));
java.sql.Timestamp ts = resultSet.getTimestamp(PUBLISH_TIME);
cal.setTime(ts);
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss z");
sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
System.out.println(sdf.format(cal.getTime()));
EDIT: to your comment:
What if I use GMT, would that be an issue in SimpleDateFormat
SimpleDateFormat can use general timezones (GMT +/- n), RFC822, and text ("if they have names" as the JavaDoc states - see this post for info on the names).