Dears,
i need your support in how to create or modify a function so as to calculate the week based on a defined day name,
by other words
i'm the one who specifies the day name from which the week starts.

HI,

If You are using MSSQL-SERVER you can use

SET DATEFIRST { number | @number_var }

Look books online for more infomation on SET DATEFIRST & @@DATEFIRST

Regards
Prashant

Dear's
kinldy be adviced that i'm using oracle DB

To my knowledge you can only use Initialization Parameter
"NLS_TERRITORY" to set the first day of week