The rates in the currency (CUR) application are yesterday's currency rates and they are updated every morning (Monday-Friday) before 08.00 CET.
The source used for this is Bloomberg: http://www.bloomberg.com/markets/currencies Quote Search.
In addition to Bloomberg, imports from the following sources are supported:
Nardowy Bank Polski
European Central Bank
The above are automatically imported into RamBase ca 04:00pm CET and will be used the next day for those companies that use this as their rate source.
On weekends or holidays when the banks are closed, the last valid exchange rate is active.