The recent Singapore case of Re Lehman Brothers Finance Asia Pte Ltd (in creditors' voluntary liquidation) determined that the debts of a company in foreign currency, which had been admitted in proof by the liquidators, were to be converted at the exchange rate prevailing at the "resolution date". In this context, resolution date means the day the resolution was passed placing the company into liquidation. The Court noted the overriding concern is to ensure equal treatment of the claims of all creditors, whether their claims are submitted in local or foreign currency by fixing the liability on the same day.
New Zealand's position on this issue is codified in section 306 of the Companies Act (1993) which provides for foreign currency claims in a liquidation to be converted into New Zealand currency at the rate of exchange on the date of commencement of the liquidation, or, if there is more than one rate of exchange on that date, at the average of those rates. The date of commencement of liquidation is defined in section 241, of the Act, which provides that liquidation commences (on the date or at the time) when a liquidator is appointed by either special resolution, by shareholders entitled to vote; or the board of the company, on the occurrence of an event specified in the constitution; or the Court, on the application of various approved people.
See Court decision here.