Console Calendar

C#

// Michael Eaton
// Tue Apr 22 2002
// Displays a calendar for a given year/month combination
// Fri Oct 11 2002
// Changed the getMonthName function based on feedback from
// Brandon Croft.

using System;
using System.Collections;
using System.Globalization;

public class myCalendar {
    public static void Main(String[] args) {
        Int16 theYear = 0;
        Int16 theMonth = 0;

        switch (args.Length) {
            case 0:
                displayCalendar();
                break;
            case 1:
                // show help
                if (args[0] == "-?" || args[0] == "/?" || args[0] == "?" || args[0] == "-h") {
                    displayUsage();
                }
                break;
            case 2:
                // see if Year is the first parameter
                if (args[0].Length > 2) {
                    theYear = Convert.ToInt16(args[0]);
                } else {
                    theYear = Convert.ToInt16(args[1]);
                }
                // be realistic
                if (theYear < 1900 || theYear > 3000) {
                    displayUsage();
                    return;
                }
                if (args[0].Length <= 2) {
                    theMonth = Convert.ToInt16(args[0]);
                } else {
                    theMonth = Convert.ToInt16(args[1]);
                }
                // only allow valid months
                if (theMonth < 1 || theMonth > 12) {
                    displayUsage();
                    return;
                }
                displayCalendar(theYear, theMonth);
                break;
            default:
                displayUsage();
                break;
        }
    }

    // help
    private static void displayUsage() {
        Console.WriteLine("Console Calendar (c) Copyright 2002 Michael Eaton");
        Console.WriteLine("usage: calendar <year> <month>");
        Console.WriteLine();
        Console.WriteLine("Year must be a 4-digit year.");
        Console.WriteLine("Month must be a number between 1 and 12.");
    }

    // the guts (overloaded methods)
    // default to the current month
    private static void displayCalendar() {
        int CurrentYear = DateTime.Today.Year;
        int CurrentMonth = DateTime.Today.Month;
        int CurrentDay = DateTime.Today.Day;
        displayCalendar(CurrentYear, CurrentMonth, CurrentDay);
    }

    private static void displayCalendar(int TheYear, int TheMonth) {
        displayCalendar(TheYear, TheMonth, 1);
    }

    private static void displayCalendar(int TheYear, int TheMonth, int TheDay) {
        // default to the first of the month
        Int16 FirstDayOfMonth = 1;
        Int32 NumberOfDaysInMonth = DateTime.DaysInMonth(TheYear, TheMonth);
        DateTime FullDateToUse = new DateTime(TheYear, TheMonth, FirstDayOfMonth);

        // this is the day of week we're gonna start with (0-6)
        Int32 StartDay = Convert.ToInt32(FullDateToUse.DayOfWeek);

        // this indicates how much padding we need for
        // the first day of the month.
        Int32 NumberOfTabs = StartDay;

        // this will display the month name and
        // the headings for the days of the week.
        displayHeader(getMonthName(TheMonth), TheYear.ToString(), true);

        // accumulator used so we'll know when to wrap
        // to the next week.
        int DayOfWeek = StartDay;
        for(int Counter = 1; Counter <= NumberOfDaysInMonth; Counter++) {
            string DayString = "";
            // if it's the first day of the month, we'll need
            // padding so we start on the correct "day"
            if (Counter == 1) {
                String Padding = new String('\t', NumberOfTabs);
                DayString = String.Concat(Padding, Counter.ToString());
            } else {
                DayString = Counter.ToString();
            }

            // highlight todays date (using *)
            if (TheDay != 1 && Counter == TheDay) {
                DayString = String.Concat("*", DayString);
            }

            // start a new line only if this isn't the first day
            if (DayOfWeek % 7 == 0 && Counter > 1) {
                DayString = String.Concat("\n", Counter.ToString());
            }

            // separate each day with a tab
            Console.Write("{0}\t", DayString);

            DayOfWeek++;
        }
        // blank line after the calendar has been printed
        Console.WriteLine();
    }

    // header for the calendar display
    private static void displayHeader(string theMonthName, string theYear, bool ShowCurrentDate) {
        // the Month, year
        string Header = String.Concat(theMonthName, ", ");
        Header = String.Concat(Header, theYear);
        String Days = "S\tM\tT\tW\tTh\tF\tS";
        String Divider = new String('-', 55);

        if (ShowCurrentDate) {
            Console.WriteLine();
            Console.WriteLine("\t\tToday is {0}/{1}/{2}.", DateTime.Today.Month, DateTime.Today.Day, DateTime.Today.Year);
        }

        Console.WriteLine();
        Console.WriteLine(String.Concat("\t\t", Header));
        Console.WriteLine(Days);
        Console.WriteLine(Divider);
    }

    private static string getMonthName(int theMonth) {
        // changes suggested by Brandon Croft.  Much shorter than
        // using the arraylist!
        DateTimeFormatInfo info = new DateTimeFormatInfo();
        string month = info.MonthNames[theMonth - 1];
        return month;
    }
}

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Save as 'calendar.cs'.
Compile at the command-line using: 'csc calendar.cs'

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