Get the First or Last Friday in a Month

Get the First or Last Friday in a Month

Perhaps it can be made quicker...

This was VERY interesting to code.

Please note that $direction is 1 for forward and -1 for backward to ease things up :)

Also, $day begins with a value of 1 for Monday and ends at 7 for Sunday.

function get_date($month, $year, $week, $day, $direction) {
  if($direction > 0)
    $startday = 1;
  else
    $startday = date('t', mktime(0, 0, 0, $month, 1, $year));

  $start = mktime(0, 0, 0, $month, $startday, $year);
  $weekday = date('N', $start);

  if($direction * $day >= $direction * $weekday)
    $offset = -$direction * 7;
  else
    $offset = 0;

  $offset += $direction * ($week * 7) + ($day - $weekday);
  return mktime(0, 0, 0, $month, $startday + $offset, $year);
}

I've tested it with a few examples and seems to work always, be sure to double-check it though ;)

Get last friday of each month in python

The easiest way to do this is to use the module dateutil:

>>> from dateutil.relativedelta import FR, relativedelta
>>> datetime.date.today()+relativedelta(day=31, weekday=FR(-1))
datetime.date(2021, 6, 25)

Don't assume you can get the last Friday of subsequent months just by adding 28 days. It won't always work. Adding 28 days to the last Friday of February 2024 gives you this:

>>> datetime.date(2024,2,1)+relativedelta(day=31, weekday=FR(-1), days=28)
datetime.date(2024, 3, 22)

but the last Friday of that month is 29 March. Let dateutil do that correctly for you:

>>> datetime.date(2024,2,1)+relativedelta(day=31, weekday=FR(-1), months=1)
datetime.date(2024, 3, 29)

How to get the next n fridays which are the first, second or third friday in a month?

You can get the ALIGNED_WEEK_OF_MONTH temporal field of the local date, and check if it is ≤ 3.

Stream.iterate(now , localDate -> localDate.with(TemporalAdjusters.next(DayOfWeek.FRIDAY)))
    .skip(1) // skip today
    .filter(x -> x.get(ChronoField.ALIGNED_WEEK_OF_MONTH) <= 3)
    .limit(10)
    .forEach(System.out::println);

How do we get the date to the last Friday of the month when the last day of the month falls on a weekend

Calculate the day number from the last day of the month.If friday(dayno =5) falls out of 5 then subtract by 5, else add 2 . Then finally subtract the days from the last day of the month if day number is 0 or 6, else return the last day of the month.

var calc = function(monthYear) {    var lastDay = moment(monthYear, "MM-YYYY").endOf("month");    var lastDayNumber = lastDay.day();    var daystoSubtract;    daystoSubtract =        lastDay.day() >= 5 ?        (daystoSubtract = lastDayNumber - 5) :        (daystoSubtract = lastDayNumber + 2);    if (lastDay.day() === 0 || lastDay.day() === 6) {        return lastDay.subtract(daystoSubtract, "days");    } else {        return lastDay;    }};
console.log(calc("05-2020").format("DD-MM-YYYY"));console.log(calc("06-2020").format("DD-MM-YYYY"));

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment.min.js"></script>

How to get the 1st date and last date of the current Week as well as Month in the format of 'yyyy-mm-dd' using App Scripts

You can use toLocaleString("sv-SE") to convert the date to the desired format yyyy-mm-dd.

Try this:

const today = new Date(); 
const firstWeekD = today.getDate() - today.getDay()-1; 
const lastWeekD = firstWeekD + 6; 
const firstdayOfWeek = new Date(today.setDate(firstWeekD)).toLocaleString("sv-SE").slice(0,10);
const lastdayOfWeek = new Date(today.setDate(lastWeekD)).toLocaleString("sv-SE").slice(0,10);
const date = new Date();
const firstDayOfMonth = new Date(date.getFullYear(), date.getMonth(), 1).toLocaleString("sv-SE").slice(0,10);
const lastDayOfMonth = new Date(date.getFullYear(), date.getMonth() + 1, 0).toLocaleString("sv-SE").slice(0,10);
  
console.log(firstdayOfWeek); // first day of the week - Saturday
console.log(lastdayOfWeek); // last day of the week - Friday
console.log(firstDayOfMonth) // first day of the month
console.log(lastDayOfMonth) // last day of the month

How to get first and last day in specific week in month

I found your week calendar approach quite amusing to play with, came up with a method that receives two parameters (month and year) and builds up the week calendar of that month:

private static Map<Integer, Integer[]> getWeekCalendar(int month, int year) {
    Map<Integer, Integer[]> weekCalendar = new HashMap<>();
    LocalDate date = LocalDate.of(year,month,1);
    int week = 1;
    LocalDate firstOfWeek = LocalDate.from(date);
    while (date.getMonth().equals(Month.of(month))) {
        //if it is a saturday, advance to the next week and register current week bounds
        if (date.getDayOfWeek().equals(DayOfWeek.SATURDAY)) {
            weekCalendar.put(week++, new Integer[]{firstOfWeek.getDayOfMonth(), date.getDayOfMonth()});
            firstOfWeek = LocalDate.from(date.plusDays(1L));
        }
        date = date.plusDays(1L);
    }
    //this one is necessary because the month may end on a Saturday
    if (firstOfWeek.getMonth().equals(Month.of(month))) {
        weekCalendar.put(week, new Integer[]{firstOfWeek.getDayOfMonth(), date.minusDays(1L).getDayOfMonth()});
    }
    return weekCalendar;
}

And a main class for testing purposes:

public static void main(String[] args) {
    int wantedMonth = 7;
    int wantedYear = 2021;
    Map<Integer, Integer[]> weekCalendar = getWeekCalendar(wantedMonth, wantedYear);
    weekCalendar.entrySet().stream()
            .map(e -> String.format("Year %d - Month %d (%s) - Week %d - First day: %d - Last day: %d", wantedYear, wantedMonth, Month.of(wantedMonth).name(), e.getKey(), e.getValue()[0], e.getValue()[1]))
            .forEach(System.out::println);
}

output:

Year 2021 - Month 7 (JULY) - Week 1 - First day: 1 - Last day: 3
Year 2021 - Month 7 (JULY) - Week 2 - First day: 4 - Last day: 10
Year 2021 - Month 7 (JULY) - Week 3 - First day: 11 - Last day: 17
Year 2021 - Month 7 (JULY) - Week 4 - First day: 18 - Last day: 24
Year 2021 - Month 7 (JULY) - Week 5 - First day: 25 - Last day: 31

Excel function to determine the last Friday in a month

The following formula achives this for a date in cell A1:

=DATE(YEAR(A1),MONTH(A1)+1,0)+MOD(-WEEKDAY(DATE(YEAR(A1),MONTH(A1)+1,0),2)-2,-7) 

How to flag last friday or last day or month

With the additional clarification and following the comment by @eminik the code below

library(data.table)
setDT(data)
data[, LastDayInMonth := day == max(day), by = .(year(day), month(day))]
data[, LastFridayInMonth := weekday == "Friday" & day == max(day), 
     by = .(year(day), month(day), weekdays(day))]

produces:

# show results (only relevant rows)
data[LastDayInMonth | LastFridayInMonth == TRUE]

          day  weekday LastDayInMonth LastFridayInMonth
1: 2016-01-29   Friday           TRUE              TRUE
2: 2016-02-26   Friday          FALSE              TRUE
3: 2016-02-29   Monday           TRUE             FALSE
4: 2016-03-25   Friday          FALSE              TRUE
5: 2016-03-31 Thursday           TRUE             FALSE
6: 2016-04-29   Friday           TRUE              TRUE
7: 2016-05-06   Friday          FALSE              TRUE
8: 2016-05-10  Tuesday           TRUE             FALSE

Edit: Code modified to account for change of years as requested by OP.

Note: weekdays returns a character vector of names in the locale in use. Therefore, the code only works if you are in an English locale. Otherwise, you may have to use Sys.setlocale(category = "LC_ALL", locale = "English") before.

Get Last Friday of Month in Java

Based on marked23's suggestion:

public Date getLastFriday( int month, int year ) {
   Calendar cal = Calendar.getInstance();
   cal.set( year, month + 1, 1 );
   cal.add( Calendar.DAY_OF_MONTH, -( cal.get( Calendar.DAY_OF_WEEK ) % 7 + 1 ) );
   return cal.getTime();
}

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