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

Question

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

User · Accepted Answer

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

User · Answer

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   gt  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   gt  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

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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

User · Answer

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

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Attention   while  calendar get Calendar DAY OF WEEK   gt  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

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public static void main String   args        System out println getMonthlyEpochList 1498867199L 12  Monthly         public static Map lt String String gt  getMonthlyEpochList Long currentEpoch  int noOfTerms  String timeMode        Map lt String String gt  map   new LinkedHashMap lt String String gt         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

User · Answer

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    gt     firstDate

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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

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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

User · Answer

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

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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   amp  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  amp  7 in ThreeTen-Backport   Android   Later versions of Android bundle implementations of the java time classes  For earlier Android   lt 26   the ThreeTenABP project adapts ThreeTen-Backport  mentioned above   See How to use ThreeTenABP

User · Answer

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     amp  amp  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     amp  amp  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     amp  amp  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   gt      belongsToCurrentDay now            final LocalDateTime yesterday   now minusDays 1           System out println  Does      toString yesterday       belong to the current day   gt      belongsToCurrentDay yesterday            final LocalDateTime tomorrow   now plusDays 1           System out println  Does      toString tomorrow       belong to the current day   gt      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   gt      belongsToCurrentWeek now            final LocalDateTime previousWeek   now minusWeeks 1           System out println  Does      toString previousWeek       belong to the current week   gt      belongsToCurrentWeek previousWeek            final LocalDateTime nextWeek   now plusWeeks 1           System out println  Does      toString nextWeek       belong to the current week   gt      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   gt      belongsToCurrentMonth now            final LocalDateTime previousMonth   now minusMonths 1           System out println  Does      toString previousMonth       belong to the current month   gt      belongsToCurrentMonth previousMonth            final LocalDateTime nextMonth   now plusMonths 1           System out println  Does      toString nextMonth       belong to the current month   gt      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   gt  true Does  2020-02-15T22 12 49 957  belong to the current day   gt  false Does  2020-02-17T22 12 49 957  belong to the current day   gt  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   gt  true Does  2020-02-09T22 12 49 957  belong to the current week   gt  false Does  2020-02-23T22 12 49 957  belong to the current week   gt  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   gt  true Does  2020-01-16T22 12 49 957  belong to the current month   gt  false Does  2020-03-16T22 12 49 957  belong to the current month   gt  false

User · Answer

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

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In this case      get today and clear time of day Calendar cal   Calendar getInstance    cal clear Calendar HOUR OF DAY     lt ---- 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

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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

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

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