We have all seen the “Earned Value Calculation” option in Admin Preferences but how it affects your Earned Value calculations?

after too many searching i found a usfel answer  it as 

BAC = BL Budgeted Labour Cost + BL Budgeted Non-Labour Cost + BL Budgeted Material Cost + BL Budgeted Expense Cost.

If the ‘Earned Value Calculation’ is set to ‘At Completion Values with Current Dates’

BAC = BL At Completion Labour Cost + BL At Completion Non-Labour Cost + BL At Completion Material Cost + BL At Completion Expense Cost.

The option of EV calculation let you adjust use of baseline dates and rules of credit