DURATION(settlement,maturity,coupon,yield,frequency,basis)
settlement: settlement date
maturity: maturity date
coupon: annual coupon rate
yield: annual yield of security
frequency: number of interest payments per year
basis: calendar basis
DURATION calculates the (Macaulay) duration of a security.
frequency may be 1 (annual), 2 (semi-annual), or 4 (quarterly). If basis is 0, then the US 30/360 method is used. If basis is 1, then actual number of days is used. If basis is 2, then actual number of days is used within a month, but years are considered only 360 days. If basis is 3, then actual number of days is used within a month, but years are always considered 365 days. If basis is 4, then the European 30/360 method is used.