exchange rates... which one?

[Morgan Read]

Hello Folk

Exchange rates - gnucash seems very capable in this area.  However,
there is a little matter I'm confused about.

I set up my accounts - I'm in the UK and I have a student loan from
NZ...  (Any Kiwi expats out their will now roll their eyes skyward
until only the whites show and then fall backwards from their stool
and lie comatose on the floor.)

So, I've started everything from a year back - well, a year an 22 days
by now.  I've entered the exchange rate for the opening balance at the
time I've started, 01.01.16.  I've set up the auto-quoting of NZD in
the Price Editor - the first entry 01.01.16 shows the source as
'user:xfer-dialog as, I assume, I entered that manually at the time of
account creation.  The following, dated this month, show the source as
'Finance::Quote' indicating that they're auto-retrieved from an online
source (v clever, impressive).

My question is, does the exchange rate used at the time of account
creation stay stuck with the transaction of that date - that is what
would have expected given when looking at that I'm looking at an
historic transaction and would expect to be looking at the historic
value of that transaction.

If the above is correct, what exchange rate is applied to (periodic)
transactions during the course of the year - for instance, penalty
interest rates applied by our beloved Inland Revenue Department?  Do I
have to update manually the exchange rate for every transaction?  If I
then hit the 'Remove Old' on the Price Editor and those exchange rates
are removed - what exchange rate is applied to the transactions which
relied on the removed exchange rate...?

Many thanks for any insight.

Regrards
Morgan

-- 
Morgan Read
P 07563-650.923
E mstuff at read.org.nz