Example of Crestron SIMPL# astronomical event scheduler

using Crestron.SimplSharp;
using Crestron.SimplSharp.Scheduler;
namespace APES.SSharp.Light
{
    public static partial class LightService 
    {
	static ScheduledEventGroup _schedule = new ScheduledEventGroup("LightService");
	static void ScheduleDuskOn(DateTime date)
        {
            string eventName = string.Format("dusk-{0}-{1}-{2}", date.Date, date.Month, date.Year);
	    //disable previous event
            if (_schedule.ScheduledEvents.ContainsKey(eventName))
            {
	    	//this might throw if event was created, but not enabled
                _schedule.ScheduledEvents[eventName].Disable();
                _schedule.ScheduledEvents[eventName].Dispose();
            }
	    //create new event and callback
            var duskEvent = new ScheduledEvent(eventName, _schedule);
            duskEvent.UserCallBack += (e, reason) =>
            {
                if (reason == ScheduledEventCommon.eCallbackReason.NormalExpiration)
                {
                    _logger.InfoFormat("Dusk event fired at {0}", DateTime.Now.ToLongTimeString());
                    ScheduleDawnOff(date.AddDays(1));
                    //do you work here
                }
            };
	    //set location, you can get it from CrestronEnviroment class
            duskEvent.Location.Latitude = _latitude;
            duskEvent.Location.Longitude = _longitude;
            duskEvent.DateAndTime.SetAstronomicalEventTime(ScheduledEventCommon.eAstronomicalEvent.Sunset, date.Year, date.Month, date.Day);
            duskEvent.Enable();
            ushort dawnHour, dawnMinute;
	    //this will throw ArgumentOutofRange if event is not valid
            ScheduledEventCommon.CalculateAstronomicalTime(duskEvent, out dawnHour, out dawnMinute);
            _logger.InfoFormat("My task is scheduled to execute at {0}:{1} {2}/{3}/{4}", dawnHour, dawnMinute, date.Date, date.Month, date.Year);
            //this will always return false for some reason, even if event is created and will fire, so catch exception above if needed
	    if (ScheduledEventCommon.isAstronomicalEventValid(duskEvent))
            {
                _logger.ErrorFormat("Dusk event is not valid! Time is {0}:{1} {2}/{3}/{4}", dawnHour, dawnMinute, date.Date, date.Month, date.Year);
            }
        }

hey @rahmanoff, checkout updated version with comments