Ref Prd Start

Function Ref Prd Start within Bond with keys Bond Ref Prd Start keysreturns the start date of the reference period of the referenced bond containing a given reference date Tˢ
Several values may be also returned here in the form of a 1D-array
Note the reference period can differ from the corresponding accrual period and is needed in the calculation of the time length of the accrual period by a few day count conventions, such as ACT/ACT(ICMA)

If the settlement date Tˢ is not explicitly given, it will be set to the bond's settlement date as implied by a trade transaction assumed to occur on the trade dateT₀ (typically today).