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Find next quarter end date given previous quarter end date using Java

I am having quarter end date of last quarter let it be 30-09-20 , the requirement is to find end date of next quarter i.e 31-12-20. I am using below code to do the same but is it giving wrong output in some scenarios. This solution should be correct for all quarters.
String str = "30-09-20";
SimpleDateFormat format = new SimpleDateFormat("dd-MM-yy");
Date date = format.parse(str);
Date newDate = DateUtils.addMonths(date, 3);
System.out.println(newDate);//Dec 30 - It should be 31 Dec

To answer your question, I think you are looking for this :
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yy");
LocalDate end = LocalDate.parse("30-09-20", formatter)
.plusMonths(3) // add three months to your date
.with(TemporalAdjusters.lastDayOfMonth()); // with the last day of the month
Note: don't use the legacy Date library, you tagged your question Java-8 which mean you can use java-time API.
Get last day of current quarter
#deHaar have reason, to get the end date of curent quarter, I would suggest to use :
public LocalDate lastDayFromDateQuarter(String date) {
final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yy");
LocalDate ld = LocalDate.parse(date, formatter);
int quarter = ld.get(IsoFields.QUARTER_OF_YEAR); // Get the Quarter, 1, 2, 3, 4
// Then create a new date with new quarter * 3 and last day of month
return ld.withMonth(quarter * 3).with(TemporalAdjusters.lastDayOfMonth());
}
Get last day of next quarter
To get the last day of the next quarter, then you just can add three months to your date like so :
public static LocalDate lastDayFromDateQuarter(String date) {
final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yy");
LocalDate ld = LocalDate.parse(date, formatter);
int quarter = ld.get(IsoFields.QUARTER_OF_YEAR);
return ld.withMonth(quarter * 3)
.plusMonths(3)
.with(TemporalAdjusters.lastDayOfMonth());
}

tl;dr
Use YearQuarter class from ThreeTen-Extra.
YearQuarter // A class available in the ThreeTen-Extra library.
.from( // Factory method rather than calling `new`.
LocalDate.of( 2020 , Month.SEPTEMBER , 30 ) // Returns a `LocalDate` object, represent a date-only value without a time-of-day and without a time zone.
) // Returns a `YearQuarter` object.
.plusQuarters( 1 ) // Perform date-math, resulting in a new `YearQuarter` object (per immutable objects pattern).
.atEndOfQuarter() // Determine the date of last day of this year-quarter.
.toString() // Generate text in standard ISO 8601 format.
2020-12-31
org.threeten.extra.YearQuarter
The ThreeTen-Extra library provides classes that extend the functionality of the java.time classes built into Java 8 and later. One of its classes is YearQuarter to represent a specific quarter in a specific year. The quarters are defined by calendar-year: Jan-Mar, Apr-June, July-Sept, Oct-Dec.
LocalDate localDate = LocalDate.of( 2020 , Month.SEPTEMBER , 30 ) ;
YearQuarter yearQuarter = YearQuarter.from( localDate ) ;
Move to the next quarter by adding one quarter to our current year-quarter.
The java.time and ThreeTen-Extra classes use immutable objects. So rather than alter ("mutate") the original object, when adding we produce a new object.
YearQuarter followingYearQuarter = yearQuarter.plusQuarters( 1 ) ;
Determine the last day of that quarter.
LocalDate lastDateOfFollowingYearQuarter = followingYearQuarter.atEndOfQuarter() ;
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Here is my version (hopefully more readable) of finding the last day of next quarter for any date:
public LocalDate lastDayOfNextQuarter(LocalDate date) {
Month firstMonthOfCurrentQuarter = date.getMonth().firstMonthOfQuarter();
LocalDate lastMonthOfCurrentQuarter = date.with(firstMonthOfCurrentQuarter.plus(2));
LocalDate lastMonthOfNextQuarter = lastMonthOfCurrentQuarter.plusMonths(3);
return lastMonthOfNextQuarter.with(lastDayOfMonth());
}
And a corresponding test method:
#ParameterizedTest
#CsvSource({"2020-01-01,2020-06-30", "2020-02-01,2020-06-30", "2020-03-01,2020-06-30", "2020-04-10,2020-09-30",
"2020-05-10,2020-09-30", "2020-06-10,2020-09-30", "2020-07-20,2020-12-31", "2020-08-20,2020-12-31",
"2020-09-30,2020-12-31", "2020-10-30,2021-03-31", "2020-11-30,2021-03-31", "2020-12-31,2021-03-31"})
public void testLastDayOfNextQuarter(LocalDate input, LocalDate expected) {
LocalDate result = timeUtils.lastDayOfNextQuarter(input);
assertEquals(expected, result);
}

You can manipulate quarter easily with TemporalAdjusters. See below:
LocalDate localDate = LocalDate.now();
LocalDate firstDayOfQuarter = localDate.with(IsoFields.DAY_OF_QUARTER, 1);
System.out.println(firstDayOfQuarter);
LocalDate lastDayOfQuarter = firstDayOfQuarter.plusMonths(2).with(TemporalAdjusters.lastDayOfMonth());
System.out.println(lastDayOfQuarter);
LocalDate firstDateOfNextQuarter = lastDayOfQuarter.plusDays(1);
LocalDate lastDayOfNextQuarter = firstDateOfNextQuarter.plusMonths(2).with(TemporalAdjusters.lastDayOfMonth());
System.out.println(lastDayOfNextQuarter);
Output:
2020-01-01
2020-03-31
2020-06-30

You can use a Calendar instance to get the last day of the month.
String str = "30-12-20";
SimpleDateFormat format = new SimpleDateFormat("dd-MM-yy");
Date date = format.parse(str);
Date newDate = DateUtils.addMonths(date, 3);
Calendar cal = new GregorianCalendar();
cal.setTime(newDate);
System.out.println(cal.getActualMaximum(Calendar.DAY_OF_MONTH));

Adding time in hours to a date object in java? [duplicate]

This question already has answers here:
Adding n hours to a date in Java?
(16 answers)
Closed 4 years ago.
How do i add hours to a date object. Below is my code:
String dateStart = timeStamp;
String dateStop = valueCon;
SimpleDateFormat format = new SimpleDateFormat("yy/MM/dd HH:mm:ss");
Date d1 = null;
Date d2 = null;
d1 = format.parse(dateStart);
d2 = format.parse(datestop);
I want to add 4 hours to d2 date object. How do i achieve it?
I tried to use :
Date modd1= new Date(d2+TimeUnit.MINUTES.toHours(240));
But it accepts only long object for adding. Thus failed.
Please support to solve this.Thanks in advance.

like others, i'd recommend using java.time if that's an option. the APIs are more consistent, and do a better job of catering to these types of operations.
however, to answer your question as-is... one option is to adjust the millisecond form of the Date instance by using get/setTime() as follows:
#Test
public void adjustTime() {
final Date date = new Date();
System.out.println("## Before adding four hours: " + date);
date.setTime(date.getTime() + TimeUnit.HOURS.toMillis(4));
System.out.println("## After adding four hours: " + date);
}
hope that helps!

If you are using java.time it can be more helpful :
LocalDateTime dateStart = LocalDateTime.now();
LocalDateTime dateStop = dateStart.plusHours(4);
To format the date you can use :
String d1 = dateStart.format(DateTimeFormatter.ofPattern("yy/MM/dd HH:mm:ss"));
String d2 = dateStop.format(DateTimeFormatter.ofPattern("yy/MM/dd HH:mm:ss"));

Well there are several ways to do
Using Calendar class
Calendar cal = Calendar.getInstance(); // creates calendar
cal.setTime(anyDateObject); // sets calendar time/date
cal.add(Calendar.HOUR_OF_DAY, 4); // adds four hour
Date date = cal.getTime(); // returns new date object
If you are using ApacheCOmmon Lang
Date newDate = DateUtils.addHours(oldDate, 3);
If you are using Joda-time
DateTime dt = new DateTime();
DateTime added = dt.plusHours(4);
and if you are using Java 8 best would be LocalDateTime
LocalDateTime startDate = LocalDateTime.now();
LocalDateTime stopdate = startDate.plusHours(4);

tl;dr
Never use Date or SimpleDateFormat classes.
Use only modern java.time classes.
Example code:
LocalDateTime.parse( // Parsing input string to an object without concept of zone or offset.
"18/01/23 12:34:56" , // Input lacking indicator of zone/offset.
DateTimeFormatter.ofPattern( "uu/MM/dd HH:mm:ss" ) // Define formatting pattern matching your input.
)
.plusHours( 4 ) // Add four hours. Generating a new `LocalDateTime` object, per immutable objects pattern.
.toString() // Generate a String in standard ISO 8601 format.
2018-01-23T16:34:56
java.time
The modern approach uses the java.time classes rather than the troublesome old legacy date-time classes. Never use Date, Calendar, SimpleDateFormat.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "uu/MM/dd HH:mm:ss" ) ;
Unzoned
Apparently your input lacks an indicator of time zone or offset-from-UTC. So parse as a LocalDateTime.
LocalDateTime ldt = LocalDateTime.parse( "18/01/23 12:34:56" ) ;
ldt.toString(): 2018-01-23T12:34:56
A LocalDateTime has no concept of time zone or offset-from-UTC. So it does not represent an actual moment, and is not a point on the timeline. A LocalDateTime is only a rough idea about potential moments along a range of about 26-27 hours.
Zoned
If you know for certain the input data was intended to represent a moment in a particular zone, apply a ZoneId to produce a ZonedDateTime. A ZonedDateTime does represent an actual moment, a point on the timeline.
ZoneId z = ZoneId.of( "Africa/Tunis" ) ;
ZonedDateTime zdt = ldt.atZone( z ) ; // Determining an actual moment.
zdt.toString(): 2018-01-23T12:34:56+01:00[Africa/Tunis]
To see the same moment in UTC, extract an Instant.
Instant instant = zdt.toInstant() ;
Math
Represent a span of time unattached to the timeline as a Duration object.
Duration d = Duration.ofHours( 4 ) ; // Four hours, as an object.
Add to your LocalDateTime, if not using time zones.
LocalDateTime ldtLater = ldt.plus( d ) ;
If using zoned values, add to your ZonedDateTime.
ZonedDateTime zdtLater = zdt.plus( d ) ;
Those classes also offer shortcut methods, if you wish.
ZonedDateTime zdtLater = zdt.plusHours( 4 ) ; // Alternative to using `Duration` object.
One benefit of using a Duration rather than the shortcut methods is having an object that can be named.
Duration halfShiftLater = Duration.ofHours( 4 ) ;
…
ZonedDateTime zdtLater = zdt.plus( halfShiftLater ) ;
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, and later
Built-in.
Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

you can do something like
Calendar c = Calendar.getInstance();
c.setTimeInMillis(d2.getTime());
c.add(Calendar.HOUR_OF_DAY, 4);
d2 = c.getTime();

I recommend you using JDK8 time API or joda-time if you can.
Old java api for date is so bad!
In your case, you can:
//commons-lang3
Date oldDate = new Date();
Date newDate = DateUtils.addHours(oldDate, 1);
OR
convert date to timestamp, add some mills and convert timestamp back to date

Retrieve Month, Day and Year values from a String using Java

How to extract Day, Month and Year values from a string [like 18/08/2012]. I tried using SimpleDateFormat, but it returns a Date object and I observed that all the Get methods are deprecated. Is there any better way to do this?
Thanks

Personally I'd use Joda Time, which makes life considerably simpler. In particular, it means you don't need to worry about the time zone of the Calendar vs the time zone of a SimpleDateFormat - you can just parse to a LocalDate, which is what the data really shows you. It also means you don't need to worry about months being 0-based :)
Joda Time makes many date/time operations much more pleasant.
import java.util.*;
import org.joda.time.*;
import org.joda.time.format.*;
public class Test {
public static void main(String[] args) throws Exception {
DateTimeFormatter formatter = DateTimeFormat.forPattern("dd/MM/yyyy")
.withLocale(Locale.UK);
LocalDate date = formatter.parseLocalDate("18/08/2012");
System.out.println(date.getYear()); // 2012
System.out.println(date.getMonthOfYear()); // 8
System.out.println(date.getDayOfMonth()); // 18
}
}

Simply go for String.split(),
String str[] = "18/08/2012".split("/");
int day = Integer.parseInt(str[0]);
int month = Integer.parseInt(str[1]);
..... and so on

This should get you going without adding external jars
SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
Date parse = sdf.parse("18/08/2012");
Calendar c = Calendar.getInstance();
c.setTime(parse);
System.out.println(c.get(Calendar.MONTH) + c.get(Calendar.DATE) + c.get(Calendar.YEAR));

Create a java.util.Calendar object out of that date as follows and extract the date parts:
Calendar cal = Calendar.getInstance();
cal.setTime(<date from simple-date-format).
cal.get(Calendar.MONTH);
etc.,

tl;dr
java.time.LocalDate.parse(
"18/08/2012" ,
DateTimeFormatter.ofPattern( "dd/MM/uuuu" )
).getDayOfMonth​() // .getYear​() .getMonth()
java.time
The modern approach uses the java.time classes. Avoid the troublesome legacy classes such as Date & Calendar.
LocalDate
String input = "18/08/2012" ;
The LocalDate class represents a date-only value without time-of-day and without time zone.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd/MM/uuuu" ) ;
LocalDate ld = LocalDate.parse( input , f ) ;
ld.toString(): 2012-08-18
Getter methods
Interrogate for the parts.
int d = ld.getDayOfMonth​() ;
int m = ld.getMonthValue() ;
int y = ld.getYear() ;
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, and later
Built-in.
Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Another approach may be use Calendar object get(Calendar.MONT)
Example:
Calendar cal = Calendar.getInstance();
cal.setTime(dateObj).
cal.get(Calendar.MONTH);
(or)
You may use String.split() also.

Use This And Pass the date Value
SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy",Locale.getDefault());
Date parse = sdf.parse("18/01/2018");
Calendar calendar = Calendar.getInstance();
calendar.setTime(parse);
int date = calendar.get(Calendar.DATE);
//+1 Is Important Because if the month is January then coming 0 so Add +1
int month = calendar.get(Calendar.MONTH)+1;
int year = calendar.get(Calendar.YEAR);
System.out.println("Date:"+date +":Month:"+ month + ":Year:"+year);

In it the String is stored in an array in form of elements, and with the help of split() function, I have separated it and retrieved it from the array str[] and stored in 3 different variables day, month & year.
import java.util.*;
public class date {
public static void main(String[] args) throws Exception {
String str[] = "18/08/2012".split("/");
int day = Integer.parseInt(str[0]);
int month = Integer.parseInt(str[1]);
int year = Integer.parseInt(str[2]);
System.out.println(day);
System.out.println(month);
System.out.println(year);
}
}

How to add 7 days to current date while not going over available days of a month?

I am trying to get todays day of the month.
And what i want to do is add seven days to the number and the get that current day of the month.
Also i want it to be able to go to the next month..Lets say today is the 29th. When it adds 7 days how can i get it to go the the next month such as 29 + 7 would equal the 5th of the next month.
How would i go about doing this?
Ive already managed to get the current date.
Calendar cal = Calendar.getInstance();
int day = cal.get(Calendar.DAY_OF_MONTH);
int dayOfMonth = day;
String today = getToday();
I am using this because i would like to launch an asynctask in my main activity every 7 days.

add(Calendar.DAY_OF_MONTH, 7);
From Calendar JavaDoc

Calendar's add method does this for you:
cal.add(Calendar.DATE, 7);
EDIT:
Given the extended comments, I guess I should add to this by saying that if cal begins as October 4, 2011, and I call cal.add(Calendar.DATE, 7) the new value of cal is October 11, 2011. Similarly, if cal begins as March 29, 2025, then after cal.add(Calendar.DATE, 7) the new value of cal is April 5, 2025.

You have to use the add method of calendar.
cal.add(Calendar.DAY_OF_MONTH, 7);

cal.add(Calendar.DAY_OF_MONTH, 7);

tl;dr
LocalDate.now( ZoneId.of( "America/Montreal" ) ) // Today’s date.
.plusWeeks( 1 ) // Yields `LocalDate` object
.getDayOfMonth() // Yields `int` number
java.time
Java 8 and later comes with the java.time framework. These new classes supplant the old java.util.Date/.Calendar classes. For older Android, see the ThreeTen-Backport and ThreeTenABP projects described below.
These classes include the LocalDate class for when you want a date-only without time-of-day and without time zone. But note that a time zone is crucial in determining the current date as a new day dawns earlier in the east.
ZoneId zoneId = ZoneId.of( "America/Montreal" );
LocalDate today = LocalDate.now( zoneId );
LocalDate weekLater = today.plusWeeks( 1 ); // Automatically rolls over between months, no problem.
If so desired, you can interrogate that LocalDate object for its day-of-month number.
int dayOfMonth = weekLater.getDayOfMonth();
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old date-time classes such as java.util.Date, .Calendar, & java.text.SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to java.time.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations.
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport and further adapted to Android in ThreeTenABP (see How to use…).
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.
Joda-Time
UPDATE: The Joda-Time project is now in maintenance mode. The team advises migration to the java.time classes. I leave this section intact as history.
In Android without Java 8 technology, you can add the Joda-Time library to your project. But know that the Joda-Time project is in maintenance mode and advises migration to java.time classes (see ThreeTenABP above for Android).
Joda-Time provided the inspiration for java.time. In this case the code needed is quite similar.
DateTimeZone zone = DateTimeZone.forID( "America/Montreal" );
LocalDate today = LocalDate.now( zone );
LocalDate weekLater = today.plusWeeks( 1 ); // Automatically rolls over between months, no problem.
int dayOfMonth = weekLater.getDayOfMonth();

Use GregorianCalendar.add(Calendar.DATE, 7). The GregorianCalendar class will take care of rolling the date into the next month.

Date m = new Date();
Calendar cal = Calendar.getInstance();
cal.setTime(m);
cal.add(Calendar.DATE, 10); // 10 is the days you want to add or subtract
m = cal.getTime();
System.out.println(m);

Date newDate = new Date(current timestamp in millis + 604800000L);//after 7 days

How to subtract X days from a date using Java calendar?

Anyone know a simple way using Java calendar to subtract X days from a date?
I have not been able to find any function which allows me to directly subtract X days from a date in Java. Can someone point me to the right direction?

Taken from the docs here:
Adds or subtracts the specified amount of time to the given calendar field, based on the calendar's rules. For example, to subtract 5 days from the current time of the calendar, you can achieve it by calling:
Calendar calendar = Calendar.getInstance(); // this would default to now
calendar.add(Calendar.DAY_OF_MONTH, -5).

You could use the add method and pass it a negative number. However, you could also write a simpler method that doesn't use the Calendar class such as the following
public static void addDays(Date d, int days)
{
d.setTime( d.getTime() + (long)days*1000*60*60*24 );
}
This gets the timestamp value of the date (milliseconds since the epoch) and adds the proper number of milliseconds. You could pass a negative integer for the days parameter to do subtraction. This would be simpler than the "proper" calendar solution:
public static void addDays(Date d, int days)
{
Calendar c = Calendar.getInstance();
c.setTime(d);
c.add(Calendar.DATE, days);
d.setTime( c.getTime().getTime() );
}
Note that both of these solutions change the Date object passed as a parameter rather than returning a completely new Date. Either function could be easily changed to do it the other way if desired.

Anson's answer will work fine for the simple case, but if you're going to do any more complex date calculations I'd recommend checking out Joda Time. It will make your life much easier.
FYI in Joda Time you could do
DateTime dt = new DateTime();
DateTime fiveDaysEarlier = dt.minusDays(5);

tl;dr
LocalDate.now().minusDays( 10 )
Better to specify time zone.
LocalDate.now( ZoneId.of( "America/Montreal" ) ).minusDays( 10 )
Details
The old date-time classes bundled with early versions of Java, such as java.util.Date/.Calendar, have proven to be troublesome, confusing, and flawed. Avoid them.
java.time
Java 8 and later supplants those old classes with the new java.time framework. See Tutorial. Defined by JSR 310, inspired by Joda-Time, and extended by theThreeTen-Extra project. The ThreeTen-Backport project back-ports the classes to Java 6 & 7; the ThreeTenABP project to Android.
The Question is vague, not clear if it asks for a date-only or a date-time.
LocalDate
For a date-only, without time-of-day, use the LocalDate class. Note that a time zone in crucial in determining a date such as "today".
LocalDate today = LocalDate.now( ZoneId.of( "America/Montreal" ) );
LocalDate tenDaysAgo = today.minusDays( 10 );
ZonedDateTime
If you meant a date-time, then use the Instant class to get a moment on the timeline in UTC. From there, adjust to a time zone to get a ZonedDateTime object.
Instant now = Instant.now(); // UTC.
ZoneId zoneId = ZoneId.of( "America/Montreal" );
ZonedDateTime zdt = ZonedDateTime.ofInstant( instant , zoneId );
ZonedDateTime tenDaysAgo = zdt.minusDays( 10 );
About java.time
The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
Java SE 8, Java SE 9, Java SE 10, and later
Built-in.
Part of the standard Java API with a bundled implementation.
Java 9 adds some minor features and fixes.
Java SE 6 and Java SE 7
Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
Android
Later versions of Android bundle implementations of the java.time classes.
For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

int x = -1;
Calendar cal = ...;
cal.add(Calendar.DATE, x);
See java.util.Calendar#add(int,int)

Instead of writing my own addDays as suggested by Eli, I would prefer to use DateUtils from Apache. It is handy especially when you have to use it multiple places in your project.
The API says:
addDays(Date date, int amount)
Adds a number of days to a date returning a new object.
Note that it returns a new Date object and does not make changes to the previous one itself.

I faced the same challenge where I needed to go back by 1 day (should be able to roll back by one even if previous day falls into previous year or months).
I did following, basically subtracted by 24 hours for 1 day.
someDateInGregorianCalendar.add(Calendar.HOUR, -24);
Alternatively, I could also do
GregorianCalendar cal = new GregorianCalendar();
cal.set(Calendar.YEAR, 2021);
cal.set(Calendar.MONTH, 0);
cal.set(Calendar.DATE, 1);
System.out.println("Original: " + cal.getTime());
cal.add(Calendar.DATE, -1);
System.out.println("After adding DATE: " + cal.getTime());
OUTPUT:
Original: Fri Jan 01 15:08:33 CET 2021
After adding DATE: Thu Dec 31 15:08:33 CET 2020

It can be done easily by the following
Calendar calendar = Calendar.getInstance();
// from current time
long curTimeInMills = new Date().getTime();
long timeInMills = curTimeInMills - 5 * (24*60*60*1000); // `enter code here`subtract like 5 days
calendar.setTimeInMillis(timeInMills);
System.out.println(calendar.getTime());
// from specific time like (08 05 2015)
calendar.set(Calendar.DAY_OF_MONTH, 8);
calendar.set(Calendar.MONTH, (5-1));
calendar.set(Calendar.YEAR, 2015);
timeInMills = calendar.getTimeInMillis() - 5 * (24*60*60*1000);
calendar.setTimeInMillis(timeInMills);
System.out.println(calendar.getTime());

I believe a clean and nice way to perform subtraction or addition of any time unit (months, days, hours, minutes, seconds, ...) can be achieved using the java.time.Instant class.
Example for subtracting 5 days from the current time and getting the result as Date:
new Date(Instant.now().minus(5, ChronoUnit.DAYS).toEpochMilli());
Another example for subtracting 1 hour and adding 15 minutes:
Date.from(Instant.now().minus(Duration.ofHours(1)).plus(Duration.ofMinutes(15)));
If you need more accuracy, Instance measures up to nanoseconds. Methods manipulating nanosecond part:
minusNano()
plusNano()
getNano()
Also, keep in mind, that Date is not as accurate as Instant. My advice is to stay within the Instant class, when possible.

Someone recommended Joda Time so - I have been using this CalendarDate class http://calendardate.sourceforge.net
It's a somewhat competing project to Joda Time, but much more basic at only 2 classes. It's very handy and worked great for what I needed since I didn't want to use a package bigger than my project. Unlike the Java counterparts, its smallest unit is the day so it is really a date (not having it down to milliseconds or something). Once you create the date, all you do to subtract is something like myDay.addDays(-5) to go back 5 days. You can use it to find the day of the week and things like that.
Another example:
CalendarDate someDay = new CalendarDate(2011, 10, 27);
CalendarDate someLaterDay = today.addDays(77);
And:
//print 4 previous days of the week and today
String dayLabel = "";
CalendarDate today = new CalendarDate(TimeZone.getDefault());
CalendarDateFormat cdf = new CalendarDateFormat("EEE");//day of the week like "Mon"
CalendarDate currDay = today.addDays(-4);
while(!currDay.isAfter(today)) {
dayLabel = cdf.format(currDay);
if (currDay.equals(today))
dayLabel = "Today";//print "Today" instead of the weekday name
System.out.println(dayLabel);
currDay = currDay.addDays(1);//go to next day
}

Eli Courtwright second solution is wrong, it should be:
Calendar c = Calendar.getInstance();
c.setTime(date);
c.add(Calendar.DATE, -days);
date.setTime(c.getTime().getTime());