Calculate number of weekdays between two dates in Java

Can anyone point me to some Java snippet wherein i can get business (except Sat and Sun) days between two dates.

Solution 1:

public static int getWorkingDaysBetweenTwoDates(Date startDate, Date endDate) {
    Calendar startCal = Calendar.getInstance();
    startCal.setTime(startDate);        

    Calendar endCal = Calendar.getInstance();
    endCal.setTime(endDate);

    int workDays = 0;

    //Return 0 if start and end are the same
    if (startCal.getTimeInMillis() == endCal.getTimeInMillis()) {
        return 0;
    }

    if (startCal.getTimeInMillis() > endCal.getTimeInMillis()) {
        startCal.setTime(endDate);
        endCal.setTime(startDate);
    }

    do {
       //excluding start date
        startCal.add(Calendar.DAY_OF_MONTH, 1);
        if (startCal.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY && startCal.get(Calendar.DAY_OF_WEEK) != Calendar.SUNDAY) {
            ++workDays;
        }
    } while (startCal.getTimeInMillis() < endCal.getTimeInMillis()); //excluding end date

    return workDays;
}

Start date and end date are exclusive, Only the days between given dates will be counted. Start date and end date will not be included.

Solution 2:

Solution without loop:

static long days(Date start, Date end){
    //Ignore argument check

    Calendar c1 = Calendar.getInstance();
    c1.setTime(start);
    int w1 = c1.get(Calendar.DAY_OF_WEEK);
    c1.add(Calendar.DAY_OF_WEEK, -w1);

    Calendar c2 = Calendar.getInstance();
    c2.setTime(end);
    int w2 = c2.get(Calendar.DAY_OF_WEEK);
    c2.add(Calendar.DAY_OF_WEEK, -w2);

    //end Saturday to start Saturday 
    long days = (c2.getTimeInMillis()-c1.getTimeInMillis())/(1000*60*60*24);
    long daysWithoutWeekendDays = days-(days*2/7);

    // Adjust days to add on (w2) and days to subtract (w1) so that Saturday
    // and Sunday are not included
    if (w1 == Calendar.SUNDAY && w2 != Calendar.SATURDAY) {
        w1 = Calendar.MONDAY;
    } else if (w1 == Calendar.SATURDAY && w2 != Calendar.SUNDAY) {
        w1 = Calendar.FRIDAY;
    } 

    if (w2 == Calendar.SUNDAY) {
        w2 = Calendar.MONDAY;
    } else if (w2 == Calendar.SATURDAY) {
        w2 = Calendar.FRIDAY;
    }

    return daysWithoutWeekendDays-w1+w2;
}

Solution 3:

Solution without loop in 5 lines of code

Days between are defined in the same way as ChronoUnit.DAYS.between(start, end) which means there are 4 days between Monday and Friday. Since we are only interested in weekdays we have to subtract weekends, therefore from Friday until Tuesday there will be 2 weekdays(just compute endDay - startDay and subtract 2 for the weekend). Add 1 to the result if you want an inclusive result, i.e. not days between.

I present two solutions.

First solution (5-liner, short and cryptic):

import java.time.*;
import java.time.temporal.*;

public static long calcWeekDays1(final LocalDate start, final LocalDate end) {
    final DayOfWeek startW = start.getDayOfWeek();
    final DayOfWeek endW = end.getDayOfWeek();

    final long days = ChronoUnit.DAYS.between(start, end);
    final long daysWithoutWeekends = days - 2 * ((days + startW.getValue())/7);

    //adjust for starting and ending on a Sunday:
    return daysWithoutWeekends + (startW == DayOfWeek.SUNDAY ? 1 : 0) + (endW == DayOfWeek.SUNDAY ? 1 : 0);
}

Second solution:

public static long calcWeekDays2(final LocalDate start, final LocalDate end) {
    final int startW = start.getDayOfWeek().getValue();
    final int endW = end.getDayOfWeek().getValue();

    final long days = ChronoUnit.DAYS.between(start, end);
    long result = days - 2*(days/7); //remove weekends

    if (days % 7 != 0) { //deal with the rest days
        if (startW == 7) {
            result -= 1;
        } else if (endW == 7) {  //they can't both be Sunday, otherwise rest would be zero
            result -= 1;
        } else if (endW < startW) { //another weekend is included
            result -= 2;
        }
    }

    return result;
}

Solution 4:

java.time

The modern way is with the java.time classes.

LocalDate

The LocalDate class represents a date-only value without time-of-day and without time zone.

LocalDate start = LocalDate.of( 2016 , 1 , 23 );
LocalDate stop = start.plusMonths( 1 );

DayOfWeek enum

The DayOfWeek enum provides a singleton instance for each of the sever days of the week.

DayOfWeek dow = start.getDayOfWeek();
if( dow.equals( DayOfWeek.SATURDAY ) || dow.equals( DayOfWeek.SUNDAY ) ) …

We can collect the desired dates in a List.

int initialCapacity = Duration.between( start , stop ).toDays() ;
List<LocalDate> dates = new ArrayList<>( initialCapacity );
…
if( dow.equals( DayOfWeek.SATURDAY ) || dow.equals( DayOfWeek.SUNDAY ) ) {
    dates.add( date );
    …

An EnumSet is an extremely efficient, fast and low-memory, implementation of Set. We can use an EnumSet instead of the if statement seen above.

Set<DayOfWeek> weekend = EnumSet.of( DayOfWeek.SATURDAY , DayOfWeek.SUNDAY ) ;
…
if( weekend.contains( dayOfWeek ) ) …

Put that all together.

LocalDate date = start ;
while( date.isBefore( stop ) ) {
    if( ! weekend.contains( date.getDayOfWeek() ) ) { // If not weekend, collect this LocalDate.
        dates.add( date ) ;
    }
    // Prepare for next loop.
    date = date.plusDays( 1 ); // Increment to next day.
}

nextWorkingDay TemporalAdjuster

Another approach uses the ThreeTen-Extra project to add classes that work with java.time.

The Temporals class adds additional implementations of TemporalAdjuster for manipulating date-time values. We want the nextWorkingDay adjuster to increment the date while skipping over Saturday & Sunday.

LocalDate start = LocalDate.of( 2016 , 1 , 23 );
LocalDate stop = start.plusMonths( 1 );

int initialCapacity = Duration.between( start , stop ).toDays() ;
List<LocalDate> dates = new ArrayList<>( initialCapacity );

LocalDate date = start.minusDays( 1 );  // Start a day ahead.
while( date.isBefore( stop ) ) {
    date = date.with( org.threeten.extra.Temporals.nextWorkingDay() );
    // Double-check ending date as the `nextWorkingDay` adjuster could move us past the stop date.
    if( date.isBefore( stop ) ) { 
        dates.add( date ) ;
    }
}

Performance

I am curious about the performance of the various approach in various Answers on this page. I am considering only the modern java.time code, not the code using troublesome legacy Date/Calendar classes.

Here are four methods that each return the number of days elapsed.

One uses the clever math-based approach seen in the Answer by Roland.

private long countWeekDaysMath ( LocalDate start , LocalDate stop ) {
    // Code taken from Answer by Roland.
    // https://stackoverflow.com/a/44942039/642706
    long count = 0;
    final DayOfWeek startW = start.getDayOfWeek();
    final DayOfWeek stopW = stop.getDayOfWeek();

    final long days = ChronoUnit.DAYS.between( start , stop );
    final long daysWithoutWeekends = days - 2 * ( ( days + startW.getValue() ) / 7 );

    //adjust for starting and ending on a Sunday:
    count = daysWithoutWeekends + ( startW == DayOfWeek.SUNDAY ? 1 : 0 ) + ( stopW == DayOfWeek.SUNDAY ? 1 : 0 );

    return count;
}

Two use approaches seen in this Answer of mine: (a) Visit each date, incrementing one-by-one in a conventional loop.

private long countWeekDaysVisit ( LocalDate start , LocalDate stop ) {
    // Code taken from Answer by Basil Bourque.
    // https://stackoverflow.com/a/40369140/642706
    long count = 0;
    Set < DayOfWeek > weekend = EnumSet.of( DayOfWeek.SATURDAY , DayOfWeek.SUNDAY );
    LocalDate ld = start;
    while ( ld.isBefore( stop ) ) {
        if ( ! weekend.contains( ld.getDayOfWeek() ) ) { // If not weekend, collect this LocalDate.
            count++;
        }
        // Prepare for next loop.
        ld = ld.plusDays( 1 ); // Increment to next day.
    }
    return count;
}

…and, (b) Using the TemporalAdjuster implementation org.threeten.extra.Temporals.nextWorkingDay().

private long countWeekDaysAdjuster ( LocalDate start , LocalDate stop ) {
    // Code taken from Answer by Basil Bourque.
    // https://stackoverflow.com/a/40369140/642706
    long count = 0;
    Set < DayOfWeek > weekend = EnumSet.of( DayOfWeek.SATURDAY , DayOfWeek.SUNDAY );
    TemporalAdjuster nextWorkingDayTA = org.threeten.extra.Temporals.nextWorkingDay();
    LocalDate ld = start;
    if ( weekend.contains( ld.getDayOfWeek() ) ) {
        ld = ld.with( nextWorkingDayTA );
    }
    while ( ld.isBefore( stop ) ) {
        count++;
        // Prepare for next loop.
        ld = ld.with( nextWorkingDayTA ); // Increment to next working day (non-weekend day).
    }
    return count;
}

The last uses Java Streams approach seen in the Answer by Ravindra Ranwala.

private long countWeekDaysStream ( LocalDate start , LocalDate stop ) {
    // Code taken from the Answer by Ravindra Ranwala.
    // https://stackoverflow.com/a/51010738/642706
    long count = 0;
    Set < DayOfWeek > weekend = EnumSet.of( DayOfWeek.SATURDAY , DayOfWeek.SUNDAY );
    final long weekDaysBetween = start.datesUntil( stop )
                                     .filter( d -> ! weekend.contains( d.getDayOfWeek() ) )
                                     .count();
    return count;
}

And the test harness.

Caveats:

• Well, the usual caveats about micro-benchmarking being untrustworthy, prone to unjustified or unrealistic conclusions.
• I wish I'd learned to use the JMH micro-benchmarking framework.
• I have not bothered to try optimizing any of this code. For example, in real work, the TemporalAdjuster could be cached outside our method.

Test harness.

LocalDate start = LocalDate.of( 2018 , Month.JANUARY , 1 );
LocalDate stop = start.plusYears( 1 );

int runs = 100_000;

long go = System.nanoTime();
for ( int i = 1 ; i <= runs ; i++ ) {
    long count = this.countWeekDaysMath( start , stop );
}
long elapsedMath = ( System.nanoTime() - go );

go = System.nanoTime();
for ( int i = 1 ; i <= runs ; i++ ) {
    long count = this.countWeekDaysVisit( start , stop );
}
long elapsedVisit = ( System.nanoTime() - go );

go = System.nanoTime();
for ( int i = 1 ; i <= runs ; i++ ) {
    long count = this.countWeekDaysStream( start , stop );
}
long elapsedAdjuster = ( System.nanoTime() - go );

go = System.nanoTime();
for ( int i = 1 ; i <= runs ; i++ ) {
    long count = this.countWeekDaysStream( start , stop );
}
long elapsedStream = ( System.nanoTime() - go );

System.out.println( "math: " + elapsedMath + " each: " + ( elapsedMath / runs ) );
System.out.println( "visit: " + elapsedVisit + " each: " + ( elapsedVisit / runs ) );
System.out.println( "adjuster: " + elapsedAdjuster + " each: " + ( elapsedAdjuster / runs ) );
System.out.println( "stream: " + elapsedStream + " each: " + ( elapsedStream / runs ) );

When run on my MacBook Pro (Sierra) with Oracle JDK 10.0.1 and ThreeTen-Extra version 1.3.2, I get results consistently close to the following. The math solution is a tiny fraction of the others at a couple hundred nanos versus several thousand, as we would expect obviously. Of the other three, the TemporalAdjuster is the longest, always over 10,000 nanos each. The visit and stream both come in well under that 10,000 nanos each, with visit being noticeably faster than streams. As seen in other examples around the internets, Java Streams usually make for nifty short code while often running significantly longer, about 20% longer in this case.

math: 18313309 each: 183

visit: 708420626 each: 7084

adjuster: 1002157240 each: 10021

stream: 924724750 each: 9247

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 java.time.

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 and 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 SE 7
• Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
• The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
• 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.

Solution 5:

I used Shengyuan Lu's solution, but I needed to make a fix for the case where the method is called when one of the dates is on a Saturday and the other a Sunday - otherwise the answer is off by a day:

static long days(Date start, Date end){
    //Ignore argument check

    Calendar c1 = GregorianCalendar.getInstance();
    c1.setTime(start);
    int w1 = c1.get(Calendar.DAY_OF_WEEK);
    c1.add(Calendar.DAY_OF_WEEK, -w1 + 1);

    Calendar c2 = GregorianCalendar.getInstance();
    c2.setTime(end);
    int w2 = c2.get(Calendar.DAY_OF_WEEK);
    c2.add(Calendar.DAY_OF_WEEK, -w2 + 1);

    //end Saturday to start Saturday 
    long days = (c2.getTimeInMillis()-c1.getTimeInMillis())/(1000*60*60*24);
    long daysWithoutSunday = days-(days*2/7);

    if (w1 == Calendar.SUNDAY) {
        w1 = Calendar.MONDAY;
    }
    if (w2 == Calendar.SUNDAY) {
        w2 = Calendar.MONDAY;
    }
    return daysWithoutSunday-w1+w2;
}