How do I output the date of all Mondays this year?

Question

I'm trying to output the dates of all Mondays this year, but my if element won't work with the conditions I'm giving it.

This is my code:

static void Main(string[] args)
{
    var dagEtt = new DateTime(DateTime.Now.Year, 1, 1);
    while (dagEtt <= DateTime.MaxValue)
    {
        if (dagEtt == DayOfWeek.Monday)
            Console.WriteLine(dagEtt);
        dagEtt = dagEtt.AddDays(1);
    }
}

Getting the dates this year, shouldn't you start sometime this year and stop sometime before `DateTime.MaxValue`, which is some 8000 years in the future? And when you find the first monday, why don't you add 7 days instead of 1? — , Sep 19 '17 at 19:08

score 1 · Answer 1 · answered Sep 19 '17 at 19:09

1

I changed your code a little bit

var start = new DateTime(DateTime.UtcNow.Year, 1, 1);
var end = start.AddYears(1);

while (start < end)
{
    if (start.DayOfWeek == DayOfWeek.Monday)
    {
        Console.WriteLine(start);
        start = start.AddDays(7);
    }
    else
    start = start.AddDays(1);
}

answered Sep 19 '17 at 19:09

tym32167

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Is it really possible that 7 days from a Monday it will be anything but a Monday? Wow – Camilo Terevinto Sep 19 '17 at 19:46
@CamiloTerevinto I know that this is not obvious, and we will have to put up with it :) – tym32167 Sep 19 '17 at 19:59
Start=start.AddDays (7+DayOfWeek.Monday-start.DayOfWeek) – Taemyr Sep 20 '17 at 06:49

score 0 · Answer 2 · answered Sep 20 '17 at 13:13

You can calculate the first Monday of the year using the % operator. This greatly simplifies your loop.

static void Main(string[] args)
{
    int year = DateTime.Now.Year;
    DateTime startDate = FirstMonday(year);

    while (startDate.Year == year)
    {
        Console.WriteLine(startDate);
        startDate = startDate.AddDays(7);
    }
}

https://stackoverflow.com/a/5665161/3194005

public static DateTime FirstMonday(int year)
{
    var firstDay = new DateTime(year, 1, 1);

    return new DateTime(year, 1, (8 - (int)firstDay.DayOfWeek) % 7 + 1);
}

How do I output the date of all Mondays this year?

2 Answers2