Return the input DateTime values current financial month, year or both

FinancialMonthYear.cs

public static int FinancialMonth(DateTime date)
{
	int month = date.Month - 3;
	if (date.Month <= 3)
	{
		month = month + 12;
	}
	return month;
}

public static int FinancialYear(DateTime date)
{
	int year = date.Year;
	if (date.Month <= 3)
	{
		year = year - 1;
	}
	return year;
}

public static string FinancialMonthYear(DateTime date, bool leadingZero = true)
{
	if(leadingZero)
	{
		return string.Format("{0:00}/{1}", FinancialMonth(date), FinancialYear(date));
	}
	else
	{
		return string.Format("{0}/{1}", FinancialMonth(date), FinancialYear(date));
	}
}

public static int FinancialQuarter(DateTime date)
{
	return ((((date.Month - 1) / 3) + 3) % 4) + 1;
}

public static DateTime FirstDayInQuarter(DateTime date)
{
	return FirstDayInQuarter(FinancialQuarter(date), date);
}

public static DateTime LastDayInQuarter(DateTime date)
{
	return LastDayInQuarter(FinancialQuarter(date), date);
}

public static DateTime FirstDayInQuarter(int quarter, DateTime date)
{
	var year = date.Year;
	if (quarter == 4)
	{
		year = year - 1;
	}
	return new DateTime(year, 1, 1).AddMonths(3 * quarter);
}

public static DateTime LastDayInQuarter(int quarter, DateTime date)
{
	var year = date.Year;
	if (quarter == 4)
	{
		year = year - 1;
	}
	return new DateTime(year, 1, 1).AddMonths((3 * quarter) + 3).AddSeconds(-1);
}

public static DateTime DateFromQuarter(int quarter, int year, bool lastDay = false)
{
	if (quarter == 4) year++;
	var date = new DateTime(year, 1, 1);
	return lastDay ? LastDayInQuarter(quarter, date) : FirstDayInQuarter(quarter, date);
}