I was needing to check for Holidays in an Appointment calendar and found some decent code that needed a bit of refactoring.
http://geekswithblogs.net/wpeck/archive/2011/12/27/us-holiday-list-in-c.aspx
static HashSet<DateTime> GetHolidays(int year) {
var holidays = new HashSet<DateTime>{
NewYears(year),
MemorialDay(year),
IndependenceDay(year),
LaborDay(year),
Thanksgiving(year),
Christmas(year)
};
var next = NextNewYears(year);
if(next != null)
holidays.Add(next.Value);
return holidays;
}
static DateTime NewYears(int year){
return AdjustForWeekendHoliday(new DateTime(year, 1, 1));
}
static DateTime IndependenceDay(int year){
return AdjustForWeekendHoliday(new DateTime(year, 7, 4));
}
///
<summary>
/// Memorial Day is the last Monday in May
/// </summary>
/// <param name="year"></param>
/// <returns></returns>
static DateTime MemorialDay(int year){
var day = new DateTime(year, 5, 31);
while (day.DayOfWeek != DayOfWeek.Monday) {
day = day.AddDays(-1);
}
return day;
}
///
<summary>
/// Labor Day is the first Monday in September
/// </summary>
/// <param name="year"></param>
/// <returns></returns>
static DateTime LaborDay(int year)
{
var day = new DateTime(year, 9, 1);
while (day.DayOfWeek != DayOfWeek.Monday) {
day = day.AddDays(1);
}
return day;
}
///
<summary>
/// Thanksgiving Day is the fourth Thursday in November
/// </summary>
/// <param name="year"></param>
/// <returns></returns>
static DateTime Thanksgiving(int year)
{
var thanksgiving = (from date in Enumerable.Range(1, 30)
where new DateTime(year, 11, date).DayOfWeek == DayOfWeek.Thursday
select date).ElementAt(3);
var day = new DateTime(year, 11, thanksgiving);
return day;
}
static DateTime Christmas(int year){
return AdjustForWeekendHoliday(new DateTime(year, 12, 25));
}
///
<summary>
/// If next year's new years is adjusted for this year, then count it
/// </summary>
/// <param name="year"></param>
/// <returns></returns>
static DateTime? NextNewYears(int year){
var day = AdjustForWeekendHoliday(new DateTime(year + 1, 1, 1));
if (day.Year == year)
return day;
return null;
}
///
<summary>
/// If the holiday falls on a Saturday, then make it Friday.
/// If the holiday falls on a Sunday, then make it Monday.
/// </summary>
/// <param name="holiday"></param>
/// <returns></returns>
public static DateTime AdjustForWeekendHoliday(DateTime holiday) {
if (holiday.DayOfWeek == DayOfWeek.Saturday) {
return holiday.AddDays(-1);
}
if (holiday.DayOfWeek == DayOfWeek.Sunday) {
return holiday.AddDays(1);
}
return holiday;
}