create a data stracture of a calendar

public static int BinarySearch(int[] array, int target)
{
    int left = 0;
    int right = array.Length - 1;
    while (left <= right)
    {
        int middle = (left + right) / 2;

        if (array[middle] == target)
            return middle;
        else if (target < array[middle])
            right = middle - 1;
        else
            left = middle + 1;
    }
    return -1;
}