[java] Get first and last day of month using threeten, LocalDate

I have a LocalDate which needs to get the first and last day of the month. How do I do that?

eg. 13/2/2014 I need to get 1/2/2014 and 28/2/2014 in LocalDate formats.

Using threeten LocalDate class.

This question is related to java date java-time

The answer is


If anyone comes looking for first day of previous month and last day of previous month:

public static LocalDate firstDayOfPreviousMonth(LocalDate date) {
        return date.minusMonths(1).withDayOfMonth(1);
    }


public static LocalDate lastDayOfPreviousMonth(LocalDate date) {
        return date.withDayOfMonth(1).minusDays(1);
    }

 LocalDate monthstart = LocalDate.of(year,month,1);
 LocalDate monthend = monthstart.plusDays(monthstart.lengthOfMonth()-1);

The API was designed to support a solution that matches closely to business requirements

import static java.time.temporal.TemporalAdjusters.*;

LocalDate initial = LocalDate.of(2014, 2, 13);
LocalDate start = initial.with(firstDayOfMonth());
LocalDate end = initial.with(lastDayOfMonth());

However, Jon's solutions are also fine.


Just here to show my implementation for @herman solution

ZoneId americaLaPazZone = ZoneId.of("UTC-04:00");

static Date firstDateOfMonth(Date date) {
  LocalDate localDate = convertToLocalDateWithTimezone(date);
  YearMonth baseMonth = YearMonth.from(localDate);
  LocalDateTime initialDate = baseMonth.atDay(firstDayOfMonth).atStartOfDay();
  return Date.from(initialDate.atZone(americaLaPazZone).toInstant());
}

static Date lastDateOfMonth(Date date) {
  LocalDate localDate = convertToLocalDateWithTimezone(date);
  YearMonth baseMonth = YearMonth.from(localDate);
  LocalDateTime lastDate = baseMonth.atEndOfMonth().atTime(23, 59, 59);
  return Date.from(lastDate.atZone(americaLaPazZone).toInstant());
}

static LocalDate convertToLocalDateWithTimezone(Date date) {
  return LocalDateTime.from(date.toInstant().atZone(americaLaPazZone)).toLocalDate();
}

Just use withDayOfMonth, and lengthOfMonth():

LocalDate initial = LocalDate.of(2014, 2, 13);
LocalDate start = initial.withDayOfMonth(1);
LocalDate end = initial.withDayOfMonth(initial.lengthOfMonth());

if you want to do it only with the LocalDate-class:

LocalDate initial = LocalDate.of(2014, 2, 13);

LocalDate start = LocalDate.of(initial.getYear(), initial.getMonthValue(),1);

// Idea: the last day is the same as the first day of next month minus one day.
LocalDate end = LocalDate.of(initial.getYear(), initial.getMonthValue(), 1).plusMonths(1).minusDays(1);

YearMonth

For completeness, and more elegant in my opinion, see this use of YearMonth class.

YearMonth month = YearMonth.from(date);
LocalDate start = month.atDay(1);
LocalDate end   = month.atEndOfMonth();

For the first & last day of the current month, this becomes:

LocalDate start = YearMonth.now().atDay(1);
LocalDate end   = YearMonth.now().atEndOfMonth();

Jon Skeets answer is right and has deserved my upvote, just adding this slightly different solution for completeness:

import static java.time.temporal.TemporalAdjusters.lastDayOfMonth;

LocalDate initial = LocalDate.of(2014, 2, 13);
LocalDate start = initial.withDayOfMonth(1);
LocalDate end = initial.with(lastDayOfMonth());

Try this:

LocalDate initial = LocalDate.of(2014, 2, 13);
LocalDate start = initial.withDayOfMonth(1);         
LocalDate end = initial.withDayOfMonth(initial.getMonthOfYear().getLastDayOfMonth(false));
System.out.println(start);
System.out.println(end);

you can find the desire output but need to take care of parameter true/false for getLastDayOfMonth method

that parameter denotes leap year


You can try this to avoid indicating custom date and if there is need to display start and end dates of current month:

    LocalDate start = LocalDate.now().minusDays(LocalDate.now().getDayOfMonth()-1);
    LocalDate end = LocalDate.now().minusDays(LocalDate.now().getDayOfMonth()).plusMonths(1);
    System.out.println("Start of month: " + start);
    System.out.println("End of month: " + end);

Result:

>     Start of month: 2019-12-01
>     End of month: 2019-12-30

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