Create Function dbo.[UDF_Gregorian_To_Persian] (@date datetime)

Returns nvarchar(50)

as

Begin

    Declare @depoch as bigint

    Declare @cycle  as bigint

    Declare @cyear  as bigint

    Declare @ycycle as bigint

    Declare @aux1 as bigint

    Declare @aux2 as bigint

    Declare @yday as bigint

    Declare @Jofst  as Numeric(18,2)

    Declare @jdn bigint

    Declare @iYear   As Integer

    Declare @iMonth  As Integer

    Declare @iDay    As Integer

    Set @Jofst=2415020.5

    Set @jdn=Round(Cast(@date as int)+ @Jofst,0)

    Set @depoch = @jdn - [dbo].[UDF_Persian_To_Julian](475, 1, 1)

    Set @cycle = Cast(@depoch / 1029983 as int)

    Set @cyear = @depoch%1029983

    If @cyear = 1029982

       Begin

         Set @ycycle = 2820

       End

    Else

       Begin

        Set @aux1 = Cast(@cyear / 366 as int)

        Set @aux2 = @cyear%366

        Set @ycycle = Cast(((2134 * @aux1) + (2816 * @aux2) + 2815) / 1028522 as int) + @aux1 + 1

      End

    Set @iYear = @ycycle + (2820 * @cycle) + 474

    If @iYear <= 0

      Begin

        Set @iYear = @iYear - 1

      End

    Set @yday = (@jdn - [dbo].[UDF_Persian_To_Julian](@iYear, 1, 1)) + 1

    If @yday <= 186

       Begin

         Set @iMonth = CEILING(Convert(Numeric(18,4),@yday) / 31)

       End

    Else

       Begin

          Set @iMonth = CEILING((Convert(Numeric(18,4),@yday) - 6) / 30) 

       End

       Set @iDay = (@jdn - [dbo].[UDF_Persian_To_Julian](@iYear, @iMonth, 1)) + 1

      Return Convert(nvarchar(50),@iDay) + '-' +   Convert(nvarchar(50),@iMonth) +'-' + Convert(nvarchar(50),@iYear)

End

GO

-- Here is the example

Select dbo.[UDF_Gregorian_To_Persian]('2012-04-18') as [Persian Date]

--Result is 30-1-1391