If you have multi-currency processing, time and expenses may be charged in different currencies at varying rates. When exchange rates alter, you can enter new rates to the Exchange Rates view, although these only apply to future entries.
Select Adjust Expense Exchange Rates or Adjust Timesheet Exchange Rates from the Financial section of the Administration menu to apply rate changes retrospectively.
Input is over two tabbed forms. Click Adjust at either one after making your settings.