Is there any reliable way to programmatically obtain (given some time t) the next weekend closing time for Dukascopy?
(...either by an API call, or by virtue of a consistent rule, or any other way.)

I know that closing time Friday is 21h00 GMT or 22h00 GMT depending on season, but how are the seasons defined? Are the boundaries between Dukascopy's summer- and winter closing regimes based on Central European Summer Time's transitions?

Market hours correspond to European Summer Time. For programmatic usage see DST related methods of:
https://docs.oracle.com/javase/1.4.2/doc ... eZone.html

Judging by historical data, calculations based on European Summer Time were wrong on Friday 16 March and Friday 23 March this year, because Dukascopy had already switched from 22h00 GMT to 21h00 GMT closing time, two weeks before European Summer Time came into effect on 25 March.

Looking at more historical data, it seems the calculation would have been wrong for quite a few weeks of each year, since Dukascopy's "summer" season appears to start earlier (in March) and end later (in October/November) than European Summer Time.

My question is:
How can my strategy know reliably (in advance) at what time Dukascopy's marketplace will close Friday?

Also: How can my strategy know reliably (in advance) at what time overnight commissions will be applied.

(BEGIN IMHO
A possible solution could be to either provide

• boolean IContext.isSummer();

or, if these policies are liable to change in future, to provide

• long IContext.settlementTimeFollowing(long t)
• long IContext.closingTimeFollowing(long t)

which can throw exceptions for t > now.
END IMHO)