If you were looking for the calendar with holidays, you can find it [here]

In this FAQ, we will go through the calculations of floating holidays, with examples.

Most programming languages have no native support for calculating floating holidays, and it is difficult to find information on how to calculate those holidays.

The examples are written in Java, but are easily translated into other similar languages.
Feel free to use the examples, as long as www.dayweekyear.com is mentioned as the source.
If you wish to use the examples server side, and not written in a blog, then it is not necessary to mention the source. If you have any questions about the examples, feel free to ask me at [ the contact page ]

Used for calculating: Easter, Ascension Day, Whit Sunday, Whit Monday, General prayer day (Danish holiday), Shrovetide, Palm Sunday and more.

Easter Sunday is the first Sunday after the 14th day of the lunar month (the nominal full moon) that falls on or after the 21 of March. The algorithm used in the calendar on www.dayweekyear.com, is based on Jean Meeus's algorithm from "Astronomical Algorithms" (1991) (Which quotes Spencer Jones and his book General Astronomy (1922) and "Journal of the British Astronomical Association (1977)").
[ Read more about calculating easter on wikipedia ]

The Easter calculation used on på www.dayweekyear.com
/** * Calculates easter * Algorithm based on the Meeus/Jones/Butcher Gregorian algorithm. * @param year The year to calculate easter * @return Calendar object with easter. */ public static GregorianCalendar calculateEaster(int year) { int Y=year; int a = Y % 19; int b = Y / 100; int c = Y % 100; int d = b / 4; int e = b % 4; int f = (b + 8) / 25; int g = (b - f + 1) / 3; int h = (19 * a + b - d - g + 15) % 30; int i = c / 4; int k = c % 4; int L = (32 + 2 * e + 2 * i - h - k) % 7; int m = (a + 11 * h + 22 * L) / 451; int month = (h + L - 7 * m + 114) / 31; int day = ((h + L - 7 * m + 114) % 31) + 1; /* * Create the gregorian calendar object. Subtract one from month, * since Gregorian calendar uses January as month 0 */ return new GregorianCalendar(year,month-1,day); }

Used for calculating: Easter, Ascension Day, Whit Sunday, Whit Monday, General Prayer Day (Danish holiday), Shrovetide, Palm Sunday and more.

During a year, a lot of holidays are depended on easter. The common thing for all of them is, they are a number of days before or after Easter. When you have the Easter calculation, it is easy to calculate the rest.
However holidays before Easter, can, in leap years, be one day before.
List of holidays depended on Easter:

Holiday	Days after Easter (before Easter has negative values)
Palm sunday	-7
Shovretide	-49 (-50 at leap years, sometimes)
Maundy Thursday	-3
Good Friday	-2
Easter monday	1
General Prayer Day	26
Ascension Day	39
Whit Monday	49
Whit Tuesday	50

Calculating holidays depended on Easter, used on www.dayweekyear.com
The method requires the Easter calculation above.
/** * Method for getting a date number of days before or after easter * @param nr The number of weekdays before (negative number) or after easter * @return GregorianCalendar with the date */ public static GregorianCalendar getEaster(int year, int nr) { //Get Easter for the requested year GregorianCalendar easterDepended=calculateEaster(year); //Add the number of days. easterDepended.add(Calendar.DAY_OF_MONTH,nr); return easterDepended; }

Used for calculations of: 1., 2., 3., 4. Sunday before Christmas and Memorial Day (United States).

The method for calculating these holidays:
Set the starting date, to the date we are going backwards from. Make a counter, which starts at the number of times the weekday occurs before the actual date.
Run the following loop: Is the date the weekday we are looking for?
If yes, subtract 1 from the counter.
If the counter is 1, return the date, otherwise subtract 1 day and repeat the loop. The loop finds the date, and the starting date (if happening on the weekday) is included in the count. If the date should not be included, start with subtracting one day from the date.


Calculation of holidays, which are the 1.,2.,3.,... specific weekday before a date, as used on www.dayweekyear.com
/** * Method for getting nr weekday before date (including date) * @param nr Number of weekday before * @param weekday The weekday we are looking for * @param dayOfMonth The date, which we are going back from * @param month The month, which we are going back from * @return GregorianCalendar with the date */ public static GregorianCalendar getNrWeekdayBefore(int year, int nr, int weekday, int dayOfMonth, int month) { //Create the start date GregorianCalendar start=new GregorianCalendar(year,month,dayOfMonth); //Initialize counter int count=1; //Test if we are below the nr. of weekdays (shouldn't happen) while(count<nr+1) { //Have we found the weekday if(start.get(Calendar.DAY_OF_WEEK)==weekday) { //Have we found the nr. weekday before. if(count==nr) return start; //Otherwise, increment the counter count=count+1; } //Add one day start.add(Calendar.DAY_OF_MONTH,-1); } //We should never get to here, but if we do, return null. return null; }

Used for: Mothers Day, All Saints Day (Sweden), Alot of holidays in Canada and USA (among those: Labors day and Thanksgiving)

This calculation is done the same way as the calculation of holidays, which are the 1.,2.,3. specific weekday before a date
An example of this holiday is Mothers Day, which occurs the second Sunday in May.
Calculation of holidays, which are the 1.,2.,3., specific weekday within a month, used on www.dayweekyear.com
/** * Method for getting a specific weekday in a month, e.g. mothers day second Sunday in May * @param nr The nr weekday to find * @param weekday The weekday, MUST be send as e.g. Calendar.SUNDAY * @param month The month we are looking for, january is 0 * @return GregorianCalendar with the date */ public static GregorianCalendar getNrWeekdayMonth(int year, int nr, int weekday, int month) { //Initialize the counter int count=1; //Initialize the date GregorianCalendar start=new GregorianCalendar(year,month,1); while(nr!=count-1) { //Have we found weekday we are looking for? if(weekday==start.get(Calendar.DAY_OF_WEEK)) { // Have we found the nr. weekday we are looking for? if(nr==count) return start; else { count=count+1; } } //Add one day start.add(Calendar.DAY_OF_MONTH,1); } //If not found, return null return null; }

Used for calculation of: Midsummer's Day (Sweden and Finland), All Saints Day (Sweden), The Queens Birthday (Australia), Early May Bank Holiday (United Kingdom), Spring Bank Holiday (Great Britain) and Summer Holiday (United Kingdom).

This is a simple calculation, start on the first date.
Run in a loop the following way:
Are we on the specific weekday?
If not, add one day (until we pass the end date)

Calculation of holidays, which are a specific weekday, between two dates, as used on www.dayweekyear.com
/** * Method for getting a date between two dates (both included) on a specific weekday. * The first occurence is returned * @param weekday The weekday to look for, must be sent as e.g. Calendar.SUNDAY * @param dayOfMonth1 The day of the month to start from * @param month1 The month to start from (january is 0) * @param dayOfMonth2 Last day of the month to check * @param month2 Last month to check (january is 0) * @return GregorianCalendar with the date */ public static GregorianCalendar getWeekdayBetween(int year, int weekday, int dayOfMonth1, int month1, int dayOfMonth2, int month2) { GregorianCalendar weekdayBetween1=new GregorianCalendar(year,month1,dayOfMonth1); GregorianCalendar weekdayBetween2=new GregorianCalendar(year,month2,dayOfMonth2); //Continue until we passed the last day while(!weekdayBetween1.after(weekdayBetween2)) { //Have we found the weekday? If yes, return if(weekdayBetween1.get(Calendar.DAY_OF_WEEK)==weekday) return weekdayBetween1; //If not add one day weekdayBetween1.add(Calendar.DAY_OF_MONTH,1); } //If not found return null; }

Used for calculation of: Extra holidays at Christmas and New Year in United Kingdom.

In United Kingdom, there is an ekstra rule for holidays. If e.g. Christmas is on a Saturday, then the next Monday is a bank holiday.
This rule is a bit complicated to calculate, but it can be done, the following way.
Create a map with every holiday during the year, except the one you wish to test.
E.g. without Christmas Day if you want to test for extra bankholiday on Christmas Day: 1. Create a map with all holidays, without Sundays and Christmas Day.
2. Test if you get an extra holiday.

The method of testing and finding the extra holiday:
Is it a Saturday, Sunday or another holiday?
If no, return nothing, since we don't have an extra holiday.
If yes, test the next day, if it is a Saturday, Sunday or another holiday, continue until it is not, and return the day.

Calculation of extra bank holidays in United Kingdom, at Christmas and New Year, used on www.dayweekyear.com
/** * Special for Great Britain, e.g. Christmas is on Saturday or Sunday, then the * following weekday without holidays, becomes holiday. * @param year The year of the holiday * @param dayOfMonth The day of month of the holiday * @param Holidays, TreeMap of holidays, with dayOfMonth_month as key and an object as value * @return GregorianCalendar with the day, otherwise null. */ public GregorianCalendar getAlwaysExtraHoliday(int year, int date, int month, TreeMap holidays) { GregorianCalendar testDay=new GregorianCalendar(year,month,date); String key=""+date+"_"+month; //Test if the date is a holiday if(testDay.get(Calendar.DAY_OF_WEEK)==Calendar.SATURDAY || testDay.get(Calendar.DAY_OF_WEEK)==Calendar.SUNDAY || holidays.get(key)!=null ) { //If yes, find next weekday, with no holiday. while(testDay.get(Calendar.DAY_OF_WEEK)==Calendar.SATURDAY || testDay.get(Calendar.DAY_OF_WEEK)==Calendar.SUNDAY || holidays.get(key)!=null ) { testDay.add(Calendar.DAY_OF_MONTH,1); key=testDay.get(Calendar.DAY_OF_MONTH)+"_"+testDay.get(Calendar.MONTH); } return testDay; } //Not a holiday, return null return null; }