A UK Vat Calculator written procedurally

NaiveVatCalculator.cs

using System;

class Program {
	static void Main() {
		WriteAmount(new DateTime(2008, 11, 01), 1.00M);
		WriteAmount(new DateTime(2009, 01, 01), 1.00M);
		WriteAmount(new DateTime(2010, 12, 01), 1.00M);
		WriteAmount(new DateTime(2011, 12, 01), 1.00M);
	}

	static void WriteAmount(DateTime date, decimal exVatAmount) {
		Console.WriteLine(string.Format("On {0:D}, for an amount of {1:c} the VAT inclusive figure is {2:c} for a rate of {3:p}", date, exVatAmount, CalculateAmount(date, exVatAmount), GetVat(date)));
	}

	static decimal GetVat(DateTime date) {
		if(date < new DateTime(2008, 12, 1)) {
			return 0.175M;
		} else if(date < new DateTime(2010, 1, 1)) {		
			return 0.15M;
		} else if(date > new DateTime(2011, 1, 4)) {
			return 0.2M;
		} else {
			return 0.175M;
		}
	}

	static decimal CalculateAmount(DateTime date, decimal exVatAmount) {
		if(date < new DateTime(2008, 12, 1)) {
			return exVatAmount * 1.175M;
		} else if(date < new DateTime(2010, 1, 1)) {		
			return exVatAmount * 1.15M;
		} else if(date > new DateTime(2011, 1, 4)) {
			return exVatAmount * 1.2M;
		} else {
			return exVatAmount * 1.175M;
		}
	}
}