An exchange rate allows Epic to convert from one currency to another. Exchange rates are only used when Epic is using multiple currencies.
Exchange rates are always recorded with a date. When Epic looks up an exchange rate it always does so with respect to a base date. It looks for an exchange rate with a date as close to but not after this base date. In purchasing the base date is generally today's date but projects have a recorded base date. This way the costs and prices on a multi-currency project do not vary. If no suitable exchange rate can be found Epic will display an error rather than the record.
Users with the 'admin' activity can add exchange rates.