Get the first day of week of a year (any programming language)

Question

How can I get the first day of the week of any given year (day being 1 to 7, or weekday name)?

I tried to figure it out in JavaScript, but I accept any other language.

I need to select a year to later build the full calendar (I thought using HTML tables and JavaScript), and for that I need to know at least the first day of the selected year.

I haven't found a solution or a question specifically dealing with finding the first day of any given year such that you only need to pass 1995, 2007, 1891. So if it's a repeated question please point the solution.

Do you have at least an online chart or DHTML site where I can see any full calendar for any year visually in that way?

The first day of any given year is January 1st...in some cultures. — hatchet - done with SOverflow, Jul 26 '11 at 19:09
@asawyer He wants the day of the week, he wrote `day being 1 to 7, or weekday name` — phlogratos, Jul 26 '11 at 19:10
possible duplicate of [JavaScript - get the first day of the week from current date](http://stackoverflow.com/questions/4156434/javascript-get-the-first-day-of-the-week-from-current-date) — Adam Liss, Apr 30 '12 at 00:47

phlogratos · Accepted Answer · 2011-07-26T19:26:13.133

4

In Javascript you can use this:

getWeekDay = function (year) {
  var d = new Date(); 
  d.setFullYear(year,0,1);
  return d.getDay()+1;
};

document.write(getWeekDay(2011));

Result is 1..7, as requested.

edited Jul 26 '11 at 19:26

answered Jul 26 '11 at 19:18

phlogratos

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2

The result will be 0-6, unless you add 1, as that's what JavaScript returns from `Date.getDay` [MDN Date Documentation](https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Date/getDay) – twip Jul 26 '11 at 19:24
Just pointing out that it returns 0 to 6. It's just a matter of adding 1 to the result to get 1 to 7. – alt.126 Jul 26 '11 at 21:20

Jon Skeet · Answer 2 · 2011-07-26T19:25:14.693

With .NET's BCL:

return new DateTime(year, 1, 1).DayOfWeek; // DayOfWeek enum value

In Noda Time:

return new LocalDate(year, 1, 1).IsoDayOfWeek; // IsoDayOfWeek enum value

In Java using the built-in classes:

Calendar calendar = Calendar.getInstance();
calendar.set(year, 1, 1);
return calendar.get(Calendar.DAY_OF_WEEK); // 1 (Sunday) - 7 (Saturday)

In Java using Joda Time:

return new LocalDate(year, 1, 1).getDayOfWeek(); // 1 (Monday) - 7 (Sunday)

Paul Sasik · Answer 3 · 2011-07-26T19:22:40.883

Pretty easy with C# and .NET:

using System;

public class SomeClass
{
    public static void Main()
    {
        DateTime dt = new DateTime(2000,1,1);
        Console.WriteLine(dt.DayOfWeek);

        dt = new DateTime(2010,1,1);
        Console.WriteLine(dt.DayOfWeek);
    }
}

Output:

Saturday 
Friday

The Java version:

import java.util.Date;
import java.util.GregorianCalendar;

public class test3
{
    public static void main (String[] args)
    {
        GregorianCalendar c = new GregorianCalendar(2000,1,1);  
        Date d = c.getTime();
        System.out.println(d.getDay());

        c = new GregorianCalendar(2010,1,1);    
        d = c.getTime();
        System.out.println(d.getDay());
    }
}

Output:

2
1

Date.getDay is deprecated, and I believe the results will depend on your time zone. Not a good idea. `c.get(Calendar.DAY_OF_WEEK)` is more appropriate. — Jon Skeet, Jul 26 '11 at 19:25

score 2 · Answer 4 · answered Jul 26 '11 at 19:14

2

At this Wikipedia article, look for Sakamoto's algorithm.

answered Jul 26 '11 at 19:14

alx

19
3

score 1 · Answer 5 · answered Jul 26 '11 at 19:11

1

This site http://5dspace-time.org/Calendar/Algorithm.html has a good explanation on how to calculate it even with pencil-and-paper

Wikipedia explains it too

answered Jul 26 '11 at 19:11

woliveirajr

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Get the first day of week of a year (any programming language)

5 Answers5