5 days per week, 24 hours per day. Examine the exchange rate for the currency you want to buy based on the currency you want to sell. Look at how values for your chosen currency pairs have fluctuated over time. Currency exchange rates are quoted in pairs of currency. The exchange quote tells you how many units of currency will receive based on the currency you want to sell. 91 means that you’ll receive 0.
The value of currencies frequently fluctuates. Anything from political instability to a natural disaster may cause a fluctuation. Make sure you understand that ratios between currencies are constantly changing. 50, will increase, you could purchase a “call contract” for a certain amount of that currency.