getting correct days

Management/Features/Calendar/CalendarMonth.cs

@@ -1,4 +1,83 @@
 public class CalendarMonth
 {
-  
+  private DateOnly firstDay { get; }
+  private int year { get => firstDay.Year; }
+  private int month { get => firstDay.Month; }
+  public IEnumerable<IEnumerable<int?>> Weeks
+  {
+    get =>
+      DaysByWeek.Select(
+        week => week.Select(d => d?.Day)
+      );
+
+  }
+
+  public IEnumerable<IEnumerable<DateTime?>> DaysByWeek
+  {
+    get
+    {
+      var weeks = new List<List<DateTime?>>();
+      var weeksInMonth = WeeksInMonth(year, month);
+      var daysInMonth = DateTime.DaysInMonth(year, month);
+
+      var firstDayOfMonth = new DateTime(year, month, 1).DayOfWeek;
+
+      var currentDay = 1;
+      for (int i = 0; i < weeksInMonth; i++)
+      {
+        var thisWeek = new List<DateTime?>();
+        if (i == 0 && firstDayOfMonth != DayOfWeek.Sunday)
+        {
+          for (int j = 0; j < 7; j++)
+          {
+            if (j < (int)firstDayOfMonth)
+            {
+              thisWeek.Add(null);
+            }
+            else
+            {
+              thisWeek.Add(new DateTime(year, month, currentDay));
+              currentDay++;
+            }
+          }
+        }
+        else
+        {
+          for (int j = 0; j < 7; j++)
+          {
+            if (currentDay <= daysInMonth)
+            {
+              thisWeek.Add(new DateTime(year, month, currentDay));
+              currentDay++;
+            }
+            else
+            {
+              thisWeek.Add(null);
+            }
+          }
+        }
+        weeks.Add(thisWeek);
+      }
+      return weeks;
+    }
+  }
+
+  public static int WeeksInMonth(int year, int month)
+  {
+    var firstDayOfMonth = new DateTime(year, month, 1).DayOfWeek;
+    var daysInMonth = DateTime.DaysInMonth(year, month);
+    var longDaysInMonth = daysInMonth + (int)(firstDayOfMonth);
+    var weeks = longDaysInMonth / 7;
+    if ((longDaysInMonth % 7) > 0)
+    {
+      weeks += 1;
+    }
+    return weeks;
+  }
+
+  public CalendarMonth(int year, int month)
+  {
+    firstDay = new DateOnly(year, month, 1);
+
+  }
 }