TimeManager.cs

using System;
//using UnityEngine;

public static class TimeManager {
	//constants for reuse below
	public const int FULL_DAY_LENGTH = 1440;
	public const int HORDE_NIGHT_FREQUENCY = 7;
	
	//these can be controlled by an external calendar script
	public static int sunrise = 240;
	public static int sunset = 1120;

	//properties for rotating the sun
	public static int DayLength {
		get {
			return sunset - sunrise;
		}
	}

	public static float SunDayRotationPerMinute {
		get {
			return 180f / DayLength;
		}
	}

	public static float SunNightRotationPerMinute {
		get {
			return 180f / (FULL_DAY_LENGTH - DayLength);
		}
	}

	//the key to this whole thing
	public static float SunRotationAmount {
		get {
			//early morning
			if (TimeOfDay <= sunrise) {
				return ((float)TimeOfDay / sunrise) * 90f;
			}

			//daytime
			if (TimeOfDay <= sunset) {
				return 90 + (TimeOfDay - sunrise) * SunDayRotationPerMinute;
			}

			//else late night
			return 270f + ( (float)(TimeOfDay - sunset) / (FULL_DAY_LENGTH - sunset)) * 90f;
		}
	}

	//check if tonight is horde night
	public static bool IsHordeNight {
		get {
			return Day % HORDE_NIGHT_FREQUENCY == 6; //6 == day 7 (zero indexed)
		}
	}

	//this increases over time
	private static int _day = 0;
	public static int Day {
		private set {
			_day = value;
		}

		get {
			return _day;
		}
	}

	private static int _timeOfDay = 0;
	public static int TimeOfDay {
		set {
			_timeOfDay = value;

			//use while, in case you increment by several days at once
			while (_timeOfDay >= FULL_DAY_LENGTH) {
				_timeOfDay -= FULL_DAY_LENGTH;
				_day++;
			}

			//check for subtraction too
			while (_timeOfDay < 0) {
				_timeOfDay += FULL_DAY_LENGTH;
				_day--;
			}
		}

		get {
			return _timeOfDay;
		}
	}

	//for testing
	public static void Main(String[] args) {
		Console.WriteLine("Running TimeManager test");
		Console.WriteLine(TimeManager.sunrise);
		Console.WriteLine(TimeManager.sunset);
		Console.WriteLine(TimeManager.DayLength);
		Console.WriteLine("---");

		Console.WriteLine(TimeManager.SunDayRotationPerMinute);
		Console.WriteLine(TimeManager.SunNightRotationPerMinute);
		Console.WriteLine("---");

		const int increment = 1;

		for (int i = 0; i < TimeManager.FULL_DAY_LENGTH; i += increment) {
			TimeManager.TimeOfDay += increment;
			Console.WriteLine("" + i + ":" + TimeManager.SunRotationAmount);

//			if (i > 250) break;
		}
	}
}