// Sunday, 15 September 1991, 02:00:00 clocks were turned backward 1 hour to
		// Sunday, 15 September 1991, 01:00:00 local standard time instead.
		// The UTC time was 14 September 1991, 17:00:00
		4: {Date(1991, September, 14, 16, 50, 0, 0, loc), Date(1991, September, 14, 7, 50, 0, 0, UTC)},
		5: {Date(1991, September, 14, 17, 0, 0, 0, loc), Date(1991, September, 14, 8, 0, 0, 0, UTC)},

	"Aug",
	"Sep",
	"Oct",
	"Nov",
	"Dec",
}

var longMonthNames = []string{
	"January",
	"February",
	"March",
	"April",
	"May",
	"June",
	"July",
	"August",
	"September",
	"October",
	"November",
	"December",
}

// match reports whether s1 and s2 match ignoring case.
// It is assumed s1 and s2 are the same length.
func match(s1, s2 string) bool {

// while the recursive call using m2 will use expNNMontgomery.
// For more details, see Ç. K. Koç, “Montgomery Reduction with Even Modulus”,
// IEE Proceedings: Computers and Digital Techniques, 141(5) 314-316, September 1994.
// http://www.people.vcu.edu/~jwang3/CMSC691/j34monex.pdf
func (z nat) expNNMontgomeryEven(x, y, m nat) nat {
	// Split m = m₁ × m₂ where m₁ = 2ⁿ
	n := m.trailingZeroBits()
	m1 := nat(nil).shl(natOne, n)

}

// A Month specifies a month of the year (January = 1, ...).
type Month int

const (
	January Month = 1 + iota
	February
	March
	April
	May
	June
	July
	August
	September
	October
	November
	December
)

// String returns the English name of the month ("January", "February", ...).
func (m Month) String() string {
	if January <= m && m <= December {