>Acording to the Bank of Canada, they fluctuate not only daily, but throughout the day as well depending on trades during time periods of the day. For instance, below is for the 23 and 24th:
>

>
>Date     23/01/06        24/01/06
>Can/US    1.1493          1.1525
>closing
>Can/US    1.1512          1.1549
>noon
>US/Can     .8687           .8659
>noon
>

>Notes:
>*Rates are expressed in Canadian dollars, converted from U.S. dollars
>*The noon exchange rate for the Canadian dollar against the U.S. dollar is calculated to reflect the trades that take place between 11:59 a.m. and 12:01 p.m. All other Canadian dollar noon exchange rates are derived from the US$/Can$ exchange rate and from indicative wholesale market quotes for a broad array of other currencies. Although obtained from sources believed to be reliable, the data are for informational purposes only, and the Bank of Canada does not guarantee their accuracy or completeness.
>
>Is the webservice you referenced using an official, information, or reference rate instead perhaps? Those rates are published once a day.

Well, it has always been my understanding that if the market closes at 1.1493, that this would be the rate during overnight and will start changing again when the market opens in the morning. From what you wrote, does this mean the rate changes overnight as well?