Develop Reference

How to select sunday before first monday of the passed month

I want to select Sunday before first Monday of the passed month.
That Sunday may be in the same month or the previous month but I want date of Sunday. I tried below logic for getting Sunday, it works for the current month but if I try passing some another month like Nov-2017 then again I have to change MONDAY-2 to MONDAY-3. So this is not the correct way. So how can I achieve this ?
Calendar c = Calendar.getInstance();
c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
System.out.println("Date " + c.getTime());
c.set(Calendar.DAY_OF_MONTH, Calendar.MONDAY - 2);
System.out.println("Date " + c.getTime());
I want to pass date to the code. So how can i do it ? like if I have date saved in variable then according to the input provided by that variable it should calculate the logic and provide the output

#Test
public void testDate() throws ParseException {
SimpleDateFormat fmt = new SimpleDateFormat("dd-MMM-yyyy");
Date d = fmt.parse("01-Nov-2017");
System.out.println(d);
Calendar c = Calendar.getInstance();
c.setTime(d);
getSundayBefore1thMondayOfMonth(c);
}
public void getSundayBefore1thMondayOfMonth(Calendar c) {
c.set(Calendar.DAY_OF_MONTH, 1);
int wd = c.get(Calendar.DAY_OF_WEEK);
if (wd > Calendar.MONDAY ) {
c.add(Calendar.DAY_OF_MONTH, 7);
}
c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
System.out.println(c.getTime());
c.add(Calendar.DAY_OF_MONTH, -1);
System.out.println(c.getTime());
}
Wed Nov 01 00:00:00 CST 2017
Mon Nov 06 00:00:00 CST 2017
Sun Nov 05 00:00:00 CST 2017

If you are using Java 8, Then you can use java.time library and you can just use :
LocalDate firstMondayOfMonth = LocalDate.now().with(
TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY)
);// This return 2018-01-01
LocalDate sunday = firstMondayOfMonth.minusDays(1);//This return 2017-12-31
To test with November 2017 you can use LocalDate.of instead LocalDate.now() like this :
LocalDate firstMondayOfMonth = LocalDate.of(2017, Month.NOVEMBER, 1).with(
TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY)
);// This return 2017-11-06
LocalDate firstSunday = firstMondayOfMonth.minusDays(1);// This return 2017-11-05

tl;dr
YearMonth
.now() // Current year-month. Tip: Better to pass the optional time zone, as shown further down in this Answer.
.atDay( 1 ) // First of the current month.
.with( TemporalAdjusters.nextOrSame( DayOfWeek.MONDAY ) ) // Move from first day of month to the following Monday, or stay on the first if it already a Monday.
.minusDays( 1 ) // Move back one day from Monday to get a Sunday. May be in current month or in previous month.
java.time
You are using troublesome old date-date classes that are now legacy, supplanted by the java.time classes.
Determining the current month means determining the current date. Determining the current date requires a time zone. For any given moment, the date varies around the globe by zone.
ZoneId z = ZoneId.of( “Africa/Tunis” ) ;
The YearMonth class represent the entire month.
YearMonth currentYearMonth = YearMonth.now( z ) ;
From that we can get the first of the month.
LocalDate firstOfMonth = currentYearMonth.atDay( 1 ) ;
We can move to a certain day of the week by calling on a TemporalAdjuster.
LocalDate firstMondayOfMonth = firstOfMonth.with( TemporalAdjusters.nextOrSame( DayOfWeek.MONDAY ) ) ;
LocalDate sundayBeforeFirstMondayOfMonth = firstMondayOfMonth.with( TemporalAdjusters.previous( DayOfWeek.SUNDAY ) ) ;
Logically, that last line could be replaced with .minusDays( 1 ) as we know the previous Sunday immediately precedes our Monday by definition.

In the code below, first we get the first monday in the month. Then we just subtract 1 day.
// input
int year = 2017;
int month = Calendar.NOVEMBER;
// get first monday of the month
Calendar c = Calendar.getInstance();
c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
c.set(Calendar.DAY_OF_WEEK_IN_MONTH, 1);
c.set(Calendar.MONTH, month);
c.set(Calendar.YEAR, year);
System.out.println("Date " + c.getTime());
// subtract 1
c.add(Calendar.DAY_OF_MONTH, -1);
System.out.println("Date " + c.getTime());

Try this:
Calendar calendar=Calendar.getInstance();
calendar.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
calendar.set(Calendar.DAY_OF_WEEK_IN_MONTH, 1);
calendar.add(Calendar.DATE, -1);
System.out.println(calendar.getTime());

Calendar c = Calendar.getInstance();
c.setFirstDayOfWeek( Calendar.MONDAY); //Monday is first day of a week
c.setMinimalDaysInFirstWeek( 1); //first week of month is the week that has at least one day in this month
//c.setMinimalDaysInFirstWeek( 7); //first week of month must be a full week
c.set(Calendar.WEEK_OF_MONTH, 1); //move to first week of month
System.out.println("Date " + c.getTime());
c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY); //move to Monday
System.out.println("Date " + c.getTime());
c.add( Calendar.DAY_OF_MONTH, -1); //go back one day
System.out.println("Date " + c.getTime());
Choose one of the c.setMinimalDaysInFirstWeek() method depending on what the first week of month means to you.

In Java 8, you can use the below code:
public static void getSundayBeforeFirstMondayOfMonth(LocalDate date){
date.with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY)).minusDays(1);
}
And, call the above method like below as per the requirement:
public static void callerMethod(){
// Call with Current Date
getSundayBeforeFirstMondayOfMonth(LocalDate.now());
//Call with Custom Date
LocalDate customDate = LocalDate.parse("27-11-2017", DateTimeFormatter.ofPattern("DD-MM-YYYY"));
getSundayBeforeFirstMondayOfMonth(customDate);
}

Get name of day from timestamp in Android

I have a class that when its initialized, it records the time of initialization in a private field with a public getter:
public class TestClass {
private long mTimestamp;
public TestClass(){
mTimestamp = System.getCurrentMillis();
}
public long getTimestamp(){
return mTimestamp;
}
}
I also have an enum with the name of days:
public enum Days implements Serializable {
MONDAY,
TUESDAY,
WEDNESDAY,
THURSDAY,
FRIDAY,
SATURDAY,
SUNDAY
}
Now the problem is in another class I have to get the timestamp and set a Days field to the day that the class was initialized:
public class OtherClass {
public Days getDayOfInitialization(TestClass testClass){
//how to do this?
Date date = new Date(testClass.getTimestamp())
Days day = Date.getDay(); //Deprecated!
//convert to enum and return...
}
}
The getDay() method of Date is deprecated...how should I do this?

If you just need the current day of week in a human-readable format, formatted to the current user's locale, then you could use this:
SimpleDateFormat sdf = new SimpleDateFormat("EEEE");
String dayString = sdf.format(new Date());
If their locale is "en_US", the output is:
Wednesday
If their locale is "de_DE", the output is:
Mittwoch
If their locale is "fr_FR", the output is:
mercredi
But if you need a numerical representation of the day of week (for example, you wanted to get '1' if it is Sunday or '2' if it is Monday), then you could use Calendar:
Calendar cal = Calendar.getInstance();
int dayInt = cal.get(Calendar.DAY_OF_WEEK);

use Calendar:
long timeStamp = testClass.getTimestamp();
Calendar c = Calendar.getInstance();
c.setTimeInMillis(timeStamp);
int dayNum = c.get(Calendar.DAY_OF_WEEK);
Days day = Days.values()[dayNum];
return day;

Standard Week
You do not need that Enum as the standard for date-time (ISO 8601) defines a week as Monday to Sunday.
Joda-Time defines constants for each day-of-week name in English such as DateTimeConstants.MONDAY.
Avoid java.util.Date
You should be using Joda-Time library, as the java.util.Date and .Calendar classes are notoriously troublesome. Joda-Time works in Android according to others.
Avoid Milliseconds As Date-Time
Tracking date-time as milliseconds is less than optimal. Serializing to a ISO 8601 string is preferable. But if you must, so be it.
Time Zone Is Crucial
Time zone is crucial. Day-of-week is defined by time zone, as the comments above discussed.
If you want UTC, Joda-Time provides the constant DateTimeZone.UTC.
Joda-Time
DateTimeZone timeZone = DateTimeZone.forID( "Europe/Paris" );
DateTime dateTime = new DateTime( millisSinceEpochInUtc, timeZone );
int dayOfWeekNumber = dateTime.getDayOfWeek(); // ISO 8601 standard says Monday is 1.
DateTimeFormatter formatter = DateTimeFormat.forPattern( "EEEE" ).withLocale( java.util.Locale.ENGLISH );
String dayOfWeekName = formatter.print( dateTime );

You should use Calendar.getInstance() method, which provide a calendar based on System Settings' TimeZone
Calendar now = Calendar.getInstance();
Then get the day of the week as an int (1 = Sunday, 2 = Monday, and so on...)
int day = now.get(Calendar.DAY_OF_WEEK);

Why is my printed date wrong?

I have verified that the date is read correctly from a file, but once I use SimpleDateFormat.format with the pattern "dd/MM/yy" it suddenly adds a month. This leads me to believe lenient mode is calculating the wrong value. But I have no idea what would make it add a full month.
Some example dates I read:
16/09/2013
23/09/2013
30/09/2013
07/10/2013
14/10/2013
21/10/2013
The code used to parse the date (it's a wrapper around Calendar I made):
public static SimpleDateTime parseDate(String date)
{
String[] dateParts = date.split("[-\\.:/]");
int day = Integer.parseInt(dateParts[0]);
int month = Integer.parseInt(dateParts[1]);
int year = Integer.parseInt(dateParts[2]);
return new SimpleDateTime(dag, maand, jaar);
}
The constructor used here:
public SimpleDateTime(int day, int month, int year)
{
date = Calendar.getInstance();
date.setLenient(true);
setDay(day);
setMonth(month);
setYear(year);
}
The setters for day, month and year:
public void setYear(int year)
{
date.set(Calendar.YEAR, year);
}
public void setMonth(int month)
{
date.set(Calendar.MONTH, month);
}
public void setDay(int day)
{
date.set(Calendar.DAY_OF_MONTH, day);
}
And the code used to format the date:
public String toString(String pattern)
{
String output = new SimpleDateFormat(pattern, Locale.getDefault()).format(date.getTime());
return output;
}
where the pattern passed is:
"dd/MM/yy"
Intended to print a date as:
16/09/13
23/09/13
Instead I get:
16/10/13
23/10/13

January is 0 in Java; February is 1 and so on.
See Calendar.JANUARY, Calendar.FEBRUARY.
So when you're reading 1 from the file
you think you read JAN but you read FEB.
You should do: date.set(Calendar.MONTH, month-1); to fix this.

Months are indexed from 0 not 1 so 10 is November and 11 will be December.
Calendar.MONTH

From documentation:
Field number for get and set indicating the month. This is a calendar-specific value. The first month of the year is JANUARY; the last depends on the number of months in a year.
So if you check JANUARY you see it starts in zero.
Make sure your month is in the interval 0-11. Possibly it is in 1-12.

The reason for this is that the counting starts at 0.
January == 0
February == 1
and so on. See the documentation.

THe problem is that you pass 9 to SimpleDateFormat and since month are indexed from 0 to 11 it will parse month '9' as the 10th month.
You need to subtract 1 from the month :)

Calendar class in Java holds months starting from 0, hence when you set the month as 0, it would consider it as January. SimpleDateFormat provides for a way to correctly display the value as 01.
Calendar cal = Calendar.getInstance();
cal.set(Calendar.MONTH, 0);
System.out.println(new SimpleDateFormat("dd/MM/yy").format(cal.getTime()));
Output:
29/01/14
The workaround for you to align you file that Calendar can work with (since December - or 12 would trickle over to the next year) or modify your logic to pick Constants like:
cal.set(Calendar.MONTH, Calendar.JANUARY);

The answer by peter.petrov is almost correct, except for one major problem. Like your question, it neglects to account for time zone.
For your information, this kind of work is much easier in Joda-Time (or new java.time.* classes in Java 8). Joda-Time is so much cleaner you won't even feel the need to create a wrapper class.
// Specify the time zone for which the incoming date is intended.
DateTimeZone timeZone = DateTimeZone.forID( "Europe/Brussels" );
String input = "16/09/2013";
DateTimeFormatter formatter = DateTimeFormat.forPattern("dd/MM/yyyy").withZone( timeZone );
DateTime dateTime = formatter.parseDateTime( input );
String output = formatter.print( dateTime );
Dump to console…
System.out.println( "dateTime: " + dateTime );
System.out.println( "output: " + output );
System.out.println( "millis since Unix epoch: " + dateTime.getMillis() );
When run…
dateTime: 2013-09-16T00:00:00.000+02:00
output: 16/09/2013
millis since Unix epoch: 1379282400000

Get first day of a particular week in Joda-Time? java

In Joda-Time, is there a way to get the date of the first day of the week(monday).
for instance i want to find out what date was this weeks monday based on todays current date 21/01/11
Cheers in advance.
edit: i also wish to find the date for the end of the week i.e sunday's date. cheers

Try LocalDate.withDayOfWeek:
LocalDate now = new LocalDate();
System.out.println(now.withDayOfWeek(DateTimeConstants.MONDAY)); //prints 2011-01-17
System.out.println(now.withDayOfWeek(DateTimeConstants.SUNDAY)); //prints 2011-01-23

LocalDate today = new LocalDate();
LocalDate weekStart = today.dayOfWeek().withMinimumValue();
LocalDate weekEnd = today.dayOfWeek().withMaximumValue();
Will give you the first and last days i.e Monday and sunday

Another option is to use roundFloorCopy. This looks like the following:
LocalDate startOfWeek = new LocalDate().weekOfWeekyear().roundFloorCopy();
For the last day of the standard week (Sunday) use roundCeilingCopy and minusDays…
LocalDate lastDateOfWeek = new LocalDate().weekOfWeekyear().roundCeilingCopy().minusDays( 1 );
Also works for DateTime. And works for end of week (exclusive).
DateTime dateTime = new DateTime();
DateTime startOfWeek = dateTime.weekOfWeekyear().roundFloorCopy();
DateTime endOfWeek = dateTime.weekOfWeekyear().roundCeilingCopy();
Dump to console…
System.out.println( "dateTime " + dateTime );
System.out.println( "startOfWeek " + startOfWeek );
System.out.println( "endOfWeek " + endOfWeek );
When run…
dateTime 2014-01-24T00:00:34.955-08:00
startOfWeek 2014-01-20T00:00:00.000-08:00
endOfWeek 2014-01-27T00:00:00.000-08:00

You can use the getDayOfWeek() method that gives you back 1 for Monday, 2 for Tue, .., 7 for Sunday in order to go back that many days and reach Monday:
import org.joda.time.DateTime;
public class JodaTest {
public static void main(String[] args) {
DateTime date = new DateTime();
System.out.println(date);
//2011-01-21T15:06:18.713Z
System.out.println(date.minusDays(date.getDayOfWeek()-1));
//2011-01-17T15:06:18.713Z
}
}

See the section "Querying DateTimes" of the Joda-Time user guide.
Here is the general algorithm I would follow:
find the day-of-week of the target date (Jan 21 2011 as you mentioned)
determine how many days ahead of Monday this is
Subtract the value of #2 from the target date using dateTime.minusDays(n)

How to get the first day of the current week and month?

I have the date of several events expressed in milliseconds[1], and I want to know which events are inside the current week and the current month, but I can't figure out how to obtain the first day (day/month/year) of the running week and convert it to milliseconds, the same for the first day of the month.
[1]Since January 1, 1970, 00:00:00 GMT

This week in milliseconds:
// get today and clear time of day
Calendar cal = Calendar.getInstance();
cal.set(Calendar.HOUR_OF_DAY, 0); // ! clear would not reset the hour of day !
cal.clear(Calendar.MINUTE);
cal.clear(Calendar.SECOND);
cal.clear(Calendar.MILLISECOND);
// get start of this week in milliseconds
cal.set(Calendar.DAY_OF_WEEK, cal.getFirstDayOfWeek());
System.out.println("Start of this week: " + cal.getTime());
System.out.println("... in milliseconds: " + cal.getTimeInMillis());
// start of the next week
cal.add(Calendar.WEEK_OF_YEAR, 1);
System.out.println("Start of the next week: " + cal.getTime());
System.out.println("... in milliseconds: " + cal.getTimeInMillis());
This month in milliseconds:
// get today and clear time of day
Calendar cal = Calendar.getInstance();
cal.set(Calendar.HOUR_OF_DAY, 0); // ! clear would not reset the hour of day !
cal.clear(Calendar.MINUTE);
cal.clear(Calendar.SECOND);
cal.clear(Calendar.MILLISECOND);
// get start of the month
cal.set(Calendar.DAY_OF_MONTH, 1);
System.out.println("Start of the month: " + cal.getTime());
System.out.println("... in milliseconds: " + cal.getTimeInMillis());
// get start of the next month
cal.add(Calendar.MONTH, 1);
System.out.println("Start of the next month: " + cal.getTime());
System.out.println("... in milliseconds: " + cal.getTimeInMillis());

The first day of week can be determined with help of java.util.Calendar as follows:
Calendar calendar = Calendar.getInstance();
calendar.clear();
calendar.setTimeInMillis(timestamp);
while (calendar.get(Calendar.DAY_OF_WEEK) > calendar.getFirstDayOfWeek()) {
calendar.add(Calendar.DATE, -1); // Substract 1 day until first day of week.
}
long firstDayOfWeekTimestamp = calendar.getTimeInMillis();
The first day of month can be determined as follows:
Calendar calendar = Calendar.getInstance();
calendar.clear();
calendar.setTimeInMillis(timestamp);
while (calendar.get(Calendar.DATE) > 1) {
calendar.add(Calendar.DATE, -1); // Substract 1 day until first day of month.
}
long firstDayOfMonthTimestamp = calendar.getTimeInMillis();
Pretty verbose, yes.
Java 7 will come with a much improved Date and Time API (JSR-310). If you can't switch yet, then you can as far use JodaTime which makes it all less complicated:
DateTime dateTime = new DateTime(timestamp);
long firstDayOfWeekTimestamp = dateTime.withDayOfWeek(1).getMillis();
and
DateTime dateTime = new DateTime(timestamp);
long firstDayOfMonthTimestamp = dateTime.withDayOfMonth(1).getMillis();

java.time
The java.time framework in Java 8 and later supplants the old java.util.Date/.Calendar classes. The old classes have proven to be troublesome, confusing, and flawed. Avoid them.
The java.time framework is inspired by the highly-successful Joda-Time library, defined by JSR 310, extended by the ThreeTen-Extra project, and explained in the Tutorial.
Instant
The Instant class represents a moment on the timeline in UTC.
The java.time framework has a resolution of nanoseconds, or 9 digits of a fractional second. Milliseconds is only 3 digits of a fractional second. Because millisecond resolution is common, java.time includes a handy factory method.
long millisecondsSinceEpoch = 1446959825213L;
Instant instant = Instant.ofEpochMilli ( millisecondsSinceEpoch );
millisecondsSinceEpoch: 1446959825213 is instant: 2015-11-08T05:17:05.213Z
ZonedDateTime
To consider current week and current month, we need to apply a particular time zone.
ZoneId zoneId = ZoneId.of ( "America/Montreal" );
ZonedDateTime zdt = ZonedDateTime.ofInstant ( instant , zoneId );
In zoneId: America/Montreal that is: 2015-11-08T00:17:05.213-05:00[America/Montreal]
Half-Open
In date-time work, we commonly use the Half-Open approach to defining a span of time. The beginning is inclusive while the ending in exclusive. Rather than try to determine the last split-second of the end of the week (or month), we get the first moment of the following week (or month). So a week runs from the first moment of Monday and goes up to but not including the first moment of the following Monday.
Let's the first day of the week, and last. The java.time framework includes a tool for that, the with method and the ChronoField enum.
By default, java.time uses the ISO 8601 standard. So Monday is the first day of the week (1) and Sunday is last (7).
ZonedDateTime firstOfWeek = zdt.with ( ChronoField.DAY_OF_WEEK , 1 ); // ISO 8601, Monday is first day of week.
ZonedDateTime firstOfNextWeek = firstOfWeek.plusWeeks ( 1 );
That week runs from: 2015-11-02T00:17:05.213-05:00[America/Montreal] to 2015-11-09T00:17:05.213-05:00[America/Montreal]
Oops! Look at the time-of-day on those values. We want the first moment of the day. The first moment of the day is not always 00:00:00.000 because of Daylight Saving Time (DST) or other anomalies. So we should let java.time make the adjustment on our behalf. To do that, we must go through the LocalDate class.
ZonedDateTime firstOfWeek = zdt.with ( ChronoField.DAY_OF_WEEK , 1 ); // ISO 8601, Monday is first day of week.
firstOfWeek = firstOfWeek.toLocalDate ().atStartOfDay ( zoneId );
ZonedDateTime firstOfNextWeek = firstOfWeek.plusWeeks ( 1 );
That week runs from: 2015-11-02T00:00-05:00[America/Montreal] to 2015-11-09T00:00-05:00[America/Montreal]
And same for the month.
ZonedDateTime firstOfMonth = zdt.with ( ChronoField.DAY_OF_MONTH , 1 );
firstOfMonth = firstOfMonth.toLocalDate ().atStartOfDay ( zoneId );
ZonedDateTime firstOfNextMonth = firstOfMonth.plusMonths ( 1 );
That month runs from: 2015-11-01T00:00-04:00[America/Montreal] to 2015-12-01T00:00-05:00[America/Montreal]
YearMonth
Another way to see if a pair of moments are in the same month is to check for the same YearMonth value.
For example, assuming thisZdt and thatZdt are both ZonedDateTime objects:
boolean inSameMonth = YearMonth.from( thisZdt ).equals( YearMonth.from( thatZdt ) ) ;
Milliseconds
I strongly recommend against doing your date-time work in milliseconds-from-epoch. That is indeed the way date-time classes tend to work internally, but we have the classes for a reason. Handling a count-from-epoch is clumsy as the values are not intelligible by humans so debugging and logging is difficult and error-prone. And, as we've already seen, different resolutions may be in play; old Java classes and Joda-Time library use milliseconds, while databases like Postgres use microseconds, and now java.time uses nanoseconds.
Would you handle text as bits, or do you let classes such as String, StringBuffer, and StringBuilder handle such details?
But if you insist, from a ZonedDateTime get an Instant, and from that get a milliseconds-count-from-epoch. But keep in mind this call can mean loss of data. Any microseconds or nanoseconds that you might have in your ZonedDateTime/Instant will be truncated (lost).
long millis = firstOfWeek.toInstant().toEpochMilli(); // Possible data loss.
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….

Attention!
while (calendar.get(Calendar.DAY_OF_WEEK) > calendar.getFirstDayOfWeek()) {
calendar.add(Calendar.DATE, -1); // Substract 1 day until first day of week.
}
is good idea, but there is some issue:
For example, i'm from Ukraine and calendar.getFirstDayOfWeek() in my country is 2 (Monday).
And today is 1 (Sunday). In this case calendar.add not called.
So, correct way is change ">" to "!=":
while (calendar.get(Calendar.DAY_OF_WEEK) != calendar.getFirstDayOfWeek()) {...

You can use the java.time package (since Java8 and late) to get start/end of day/week/month.
The util class example below:
import org.junit.Test;
import java.time.DayOfWeek;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.time.temporal.TemporalAdjusters;
import java.util.Date;
public class DateUtil {
private static final ZoneId DEFAULT_ZONE_ID = ZoneId.of("UTC");
public static LocalDateTime startOfDay() {
return LocalDateTime.now(DEFAULT_ZONE_ID).with(LocalTime.MIN);
}
public static LocalDateTime endOfDay() {
return LocalDateTime.now(DEFAULT_ZONE_ID).with(LocalTime.MAX);
}
public static boolean belongsToCurrentDay(final LocalDateTime localDateTime) {
return localDateTime.isAfter(startOfDay()) && localDateTime.isBefore(endOfDay());
}
//note that week starts with Monday
public static LocalDateTime startOfWeek() {
return LocalDateTime.now(DEFAULT_ZONE_ID)
.with(LocalTime.MIN)
.with(TemporalAdjusters.previousOrSame(DayOfWeek.MONDAY));
}
//note that week ends with Sunday
public static LocalDateTime endOfWeek() {
return LocalDateTime.now(DEFAULT_ZONE_ID)
.with(LocalTime.MAX)
.with(TemporalAdjusters.nextOrSame(DayOfWeek.SUNDAY));
}
public static boolean belongsToCurrentWeek(final LocalDateTime localDateTime) {
return localDateTime.isAfter(startOfWeek()) && localDateTime.isBefore(endOfWeek());
}
public static LocalDateTime startOfMonth() {
return LocalDateTime.now(DEFAULT_ZONE_ID)
.with(LocalTime.MIN)
.with(TemporalAdjusters.firstDayOfMonth());
}
public static LocalDateTime endOfMonth() {
return LocalDateTime.now(DEFAULT_ZONE_ID)
.with(LocalTime.MAX)
.with(TemporalAdjusters.lastDayOfMonth());
}
public static boolean belongsToCurrentMonth(final LocalDateTime localDateTime) {
return localDateTime.isAfter(startOfMonth()) && localDateTime.isBefore(endOfMonth());
}
public static long toMills(final LocalDateTime localDateTime) {
return localDateTime.atZone(DEFAULT_ZONE_ID).toInstant().toEpochMilli();
}
public static Date toDate(final LocalDateTime localDateTime) {
return Date.from(localDateTime.atZone(DEFAULT_ZONE_ID).toInstant());
}
public static String toString(final LocalDateTime localDateTime) {
return localDateTime.format(DateTimeFormatter.ISO_DATE_TIME);
}
#Test
public void test() {
//day
final LocalDateTime now = LocalDateTime.now();
System.out.println("Now: " + toString(now) + ", in mills: " + toMills(now));
System.out.println("Start of day: " + toString(startOfDay()));
System.out.println("End of day: " + toString(endOfDay()));
System.out.println("Does '" + toString(now) + "' belong to the current day? > " + belongsToCurrentDay(now));
final LocalDateTime yesterday = now.minusDays(1);
System.out.println("Does '" + toString(yesterday) + "' belong to the current day? > " + belongsToCurrentDay(yesterday));
final LocalDateTime tomorrow = now.plusDays(1);
System.out.println("Does '" + toString(tomorrow) + "' belong to the current day? > " + belongsToCurrentDay(tomorrow));
//week
System.out.println("Start of week: " + toString(startOfWeek()));
System.out.println("End of week: " + toString(endOfWeek()));
System.out.println("Does '" + toString(now) + "' belong to the current week? > " + belongsToCurrentWeek(now));
final LocalDateTime previousWeek = now.minusWeeks(1);
System.out.println("Does '" + toString(previousWeek) + "' belong to the current week? > " + belongsToCurrentWeek(previousWeek));
final LocalDateTime nextWeek = now.plusWeeks(1);
System.out.println("Does '" + toString(nextWeek) + "' belong to the current week? > " + belongsToCurrentWeek(nextWeek));
//month
System.out.println("Start of month: " + toString(startOfMonth()));
System.out.println("End of month: " + toString(endOfMonth()));
System.out.println("Does '" + toString(now) + "' belong to the current month? > " + belongsToCurrentMonth(now));
final LocalDateTime previousMonth = now.minusMonths(1);
System.out.println("Does '" + toString(previousMonth) + "' belong to the current month? > " + belongsToCurrentMonth(previousMonth));
final LocalDateTime nextMonth = now.plusMonths(1);
System.out.println("Does '" + toString(nextMonth) + "' belong to the current month? > " + belongsToCurrentMonth(nextMonth));
}
}
Test output:
Now: 2020-02-16T22:12:49.957, in mills: 1581891169957
Start of day: 2020-02-16T00:00:00
End of day: 2020-02-16T23:59:59.999999999
Does '2020-02-16T22:12:49.957' belong to the current day? > true
Does '2020-02-15T22:12:49.957' belong to the current day? > false
Does '2020-02-17T22:12:49.957' belong to the current day? > false
Start of week: 2020-02-10T00:00:00
End of week: 2020-02-16T23:59:59.999999999
Does '2020-02-16T22:12:49.957' belong to the current week? > true
Does '2020-02-09T22:12:49.957' belong to the current week? > false
Does '2020-02-23T22:12:49.957' belong to the current week? > false
Start of month: 2020-02-01T00:00:00
End of month: 2020-02-29T23:59:59.999999999
Does '2020-02-16T22:12:49.957' belong to the current month? > true
Does '2020-01-16T22:12:49.957' belong to the current month? > false
Does '2020-03-16T22:12:49.957' belong to the current month? > false

I have created some methods for this:
public static String catchLastDayOfCurrentWeek(String pattern) {
Calendar cal = Calendar.getInstance();
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.clear(Calendar.MINUTE);
cal.clear(Calendar.SECOND);
cal.clear(Calendar.MILLISECOND);
cal.set(Calendar.DAY_OF_WEEK, cal.getFirstDayOfWeek());
return calendarToString(cal, pattern);
}
public static String catchLastDayOfCurrentWeek(String pattern) {
Calendar cal = Calendar.getInstance();
cal.set(Calendar.HOUR_OF_DAY, 0);
cal.clear(Calendar.MINUTE);
cal.clear(Calendar.SECOND);
cal.clear(Calendar.MILLISECOND);
cal.set(Calendar.DAY_OF_WEEK, cal.getFirstDayOfWeek());
cal.add(Calendar.WEEK_OF_YEAR, 1);
cal.add(Calendar.MILLISECOND, -1);
return calendarToString(cal, pattern);
}
public static String catchTheFirstDayOfThemonth(Integer month, pattern padrao) {
Calendar cal = GregorianCalendar.getInstance();
cal.setTime(new Date());
cal.set(Calendar.MONTH, month);
cal.set(Calendar.DAY_OF_MONTH, 1);
return calendarToString(cal, pattern);
}
public static String catchTheLastDayOfThemonth(Integer month, String pattern) {
Calendar cal = GregorianCalendar.getInstance();
cal.setTime(new Date());
cal.set(cal.get(Calendar.YEAR), month, cal.getActualMaximum(Calendar.DAY_OF_MONTH));
return calendarToString(cal, pattern);
}
public static String calendarToString(Calendar calendar, String pattern) {
if (calendar == null) {
return "";
}
SimpleDateFormat format = new SimpleDateFormat(pattern, LocaleUtils.DEFAULT_LOCALE);
return format.format(calendar.getTime());
}
You can see more here.

To get the first day of the month, simply get a Date and set the current day to day 1 of the month. Clear hour, minute, second and milliseconds if you need it.
private static Date firstDayOfMonth(Date date) {
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.set(Calendar.DATE, 1);
return calendar.getTime();
}
First day of the week is the same thing, but using Calendar.DAY_OF_WEEK instead
private static Date firstDayOfWeek(Date date) {
Calendar calendar = Calendar.getInstance();
calendar.setTime(date);
calendar.set(Calendar.DAY_OF_WEEK, 1);
return calendar.getTime();
}

In this case:
// get today and clear time of day
Calendar cal = Calendar.getInstance();
cal.clear(Calendar.HOUR_OF_DAY); <---- is the current hour not 0 hour
cal.clear(Calendar.MINUTE);
cal.clear(Calendar.SECOND);
cal.clear(Calendar.MILLISECOND);
So the Calendar.HOUR_OF_DAY returns 8, 9, 12, 15, 18 as the current running hour.
I think will be better change such line by:
c.set(Calendar.HOUR_OF_DAY,0);
this way the day always begin at 0 hour

Get First date of next month:-
SimpleDateFormat df = new SimpleDateFormat("MM-dd-yyyy");
String selectedDate="MM-dd-yyyy like 07-02-2018";
Date dt = df.parse(selectedDate);`enter code here`
calendar = Calendar.getInstance();
calendar.setTime(dt);
calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMaximum(Calendar.DAY_OF_MONTH) + 1);
String firstDate = df.format(calendar.getTime());
System.out.println("firstDateof next month ==>" + firstDate);

A one-line solution using Java 8 features
In Java
LocalDateTime firstOfWeek = LocalDateTime.now().with(ChronoField.DAY_OF_WEEK, 1).toLocalDate().atStartOfDay(); // 2020-06-08 00:00 MONDAY
LocalDateTime firstOfMonth = LocalDateTime.now().with(ChronoField.DAY_OF_MONTH , 1).toLocalDate().atStartOfDay(); // 2020-06-01 00:00
// Convert to milliseconds:
firstOfWeek.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli();
In Kotlin
val firstOfWeek = LocalDateTime.now().with(ChronoField.DAY_OF_WEEK, 1).toLocalDate().atStartOfDay() // 2020-06-08 00:00 MONDAY
val firstOfMonth = LocalDateTime.now().with(ChronoField.DAY_OF_MONTH , 1).toLocalDate().atStartOfDay() // 2020-06-01 00:00
// Convert to milliseconds:
firstOfWeek.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli()

You should be able to convert your number to a Java Calendar, e.g.:
Calendar.getInstance().setTimeInMillis(myDate);
From there, the comparison shouldn't be too hard.

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.Scanner;
/**
This Program will display day for, 1st and last days in a given month and year
#author Manoj Kumar Dunna
Mail Id : manojdunna#gmail.com
*/
public class DayOfWeek {
public static void main(String[] args) {
String strDate = null;
int year = 0, month = 0;
Scanner sc = new Scanner(System.in);
System.out.print("Enter YYYY/MM: ");
strDate = sc.next();
Calendar cal = new GregorianCalendar();
String [] date = strDate.split("/");
year = Integer.parseInt(date[0]);
month = Integer.parseInt(date[1]);
cal.set(year, month-1, 1);
System.out.println(new SimpleDateFormat("EEEE").format(cal.getTime()));
cal.add(Calendar.MONTH, 1);
cal.add(Calendar.DAY_OF_YEAR, -1);
System.out.println(new SimpleDateFormat("EEEE").format(cal.getTime()));
}
}

Simple Solution:
package com.util.calendarutil;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
public class CalUtil {
public static void main(String args[]){
DateFormat df = new SimpleDateFormat("dd/mm/yyyy");
Date dt = null;
try {
dt = df.parse("23/01/2016");
} catch (ParseException e) {
System.out.println("Error");
}
Calendar cal = Calendar.getInstance();
cal.setTime(dt);
cal.set(Calendar.DAY_OF_WEEK, cal.getFirstDayOfWeek());
Date startDate = cal.getTime();
cal.add(Calendar.DATE, 6);
Date endDate = cal.getTime();
System.out.println("Start Date:"+startDate+"End Date:"+endDate);
}
}

i use this trick to get the first day of the current month
note the order is
1 for Sunday
2 for Monday
3 for Tuesday
.... and so on
Calendar cal = new GregorianCalendar();
int startDay = cal.get(Calendar.DAY_OF_YEAR) % 7 + 1;
System.out.println(startDay);

public static void main(String[] args) {
System.out.println(getMonthlyEpochList(1498867199L,12,"Monthly"));
}
public static Map<String,String> getMonthlyEpochList(Long currentEpoch, int noOfTerms, String timeMode) {
Map<String,String> map = new LinkedHashMap<String,String>();
int month = 0;
while(noOfTerms != 0) {
Calendar calendar = Calendar.getInstance();
calendar.add(Calendar.MONTH, month);
calendar.set(Calendar.DATE, calendar.getActualMinimum(Calendar.DAY_OF_MONTH));
Date monthFirstDay = calendar.getTime();
calendar.set(Calendar.DATE, calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
Date monthLastDay = calendar.getTime();
map.put(getMMYY(monthFirstDay.getTime()), monthFirstDay + ":" +monthLastDay);
month--;
noOfTerms--;
}
return map;
}