How to get the days of the next month?

Question

What I'm trying to achieve

I'm trying to get the number of days of two months (the current) and the next month. Actually I succesfully achieve this, using that code:

int monthDays = DateTime.DaysInMonth(DateTime.Now.Year, DateTime.Now.Month);
string[] days = Enumerable.Range(1, monthDays).Select(x => x.ToString("D2")).ToArray();

essentially I used the function DaysInMonth and then I generated a List<int> that represents the days of that month.

Problem

Now, I want get also the days of the next month, but I've some problem to handle the following situation:

December 2018 (current)
January 2019 (next)

What I tried

as you can see the year has changed, so the code that I wrote for get the days of next months will fail:

var nextMonth = new DateTime(DateTime.Now.Year, DateTime.Now.Month, 1).AddMonths(1);
monthDays = DateTime.DaysInMonth(DateTime.Now.Year, nextMonth.Month);
days = Enumerable.Range(1, monthDays).Select(x => x.ToString("D2")).ToArray();

how can I manage the new year in the next month?

You know how you're accessing `nextMonth.Month` to obtain *its* month rather than using `DateTime.Now`? Why aren't you doing the same for `Year`? — Damien_The_Unbeliever, Jul 27 '18 at 11:56
as @Damien_The_Unbeliever suggested, use `monthDays = DateTime.DaysInMonth(nextMonth.Year, nextMonth.Month);` — Liu, Jul 27 '18 at 11:58
what is your definition of "the days in the month"? Like Mon, Tues... or 1,2,3? — Liam, Jul 27 '18 at 11:58
@Damien_The_Unbeliever I was looking for another way to achieve that (my solution is heavy enough for a simple thing) — Charanoglu, Jul 27 '18 at 11:59
Possible duplicate of [Getting number of days in a month](https://stackoverflow.com/questions/4832468/getting-number-of-days-in-a-month) — Liam, Jul 27 '18 at 11:59
Cos you know that this is just in the framework [`DateTime.DaysInMonth`](https://stackoverflow.com/questions/4832468/getting-number-of-days-in-a-month) — Liam, Jul 27 '18 at 12:00
@Charanoglu - you literally *type less* to use `nextMonth.Year` in that final call than `DateTime.Now.Year`. — Damien_The_Unbeliever, Jul 27 '18 at 12:00
Also, I'm guessing you avoided doing `DateTime.Now.AddMonths(1)` to avoid overflows? Be aware that [AddMonths](https://msdn.microsoft.com/en-us/library/system.datetime.addmonths(v=vs.110).aspx#Remarks) already takes care of this: "If the resulting day is not a valid day in the resulting month, the last valid day of the resulting month is used. " — Damien_The_Unbeliever, Jul 27 '18 at 12:04
@Damien_The_Unbeliever yep, I had a bit of trouble in the past using it — Charanoglu, Jul 27 '18 at 12:06

aloisdg · Accepted Answer · 2018-07-27T12:07:51.943

Use AddMonth() to ... add a month. Finally, use DaysInMonth to get the number of days in the specified month and year.

public static void Main()
{
    // 12 for december as example
    var current = new DateTime(DateTime.Now.Year, 12, DateTime.Now.Day);
    var next  = current.AddMonths(1);
    Console.WriteLine(DateTime.DaysInMonth(next.Year, next.Month));
}

Output

Try it Online!

Bonus: you can read the AddMonth() source.

Gerald Chifanzwa · Answer 2 · 2018-07-27T12:24:09.533

-2

    public int GetDaysInMonth(DateTime date)
    {
        return DateTime.DaysInMonth(date.Year, date.Month);
    }

    public int GetDaysInNextMonth(DateTime date)
    {
                    //Adding months will automatically sort out the year if need be
        var nextMonth = date.AddMonths(1);
        return DateTime.DaysInMonth(nextMonthDate.Year, nextMonthDate.Month);
    }

edited Jul 27 '18 at 12:24

answered Jul 27 '18 at 12:09

Gerald Chifanzwa

1,277
7
14

What does the ensuring do here? You never use those vars? Why do you want to *Ensure we are dealing with day 1 of month to take care of those 30, 31 days*? The baked in method does all this for you if your trying to throw exceptions – Liam Jul 27 '18 at 12:11
@Liam good point. AddMonths() doesnt overflow to the next month if next month has less days...had missed that one – Gerald Chifanzwa Jul 27 '18 at 12:21

How to get the days of the next month?

2 Answers2