I wrote to the Commonwealth WarGraves Commission to enquire whether there was a cut-off point for commemoration of the war dead with a CWGC stone. I received the following reply.
15 March 2010
Dear Mr Smith
Thank you for your e-mail of 29 January 2010.
I would explain that the Commission is responsible for the commemoration of serving members of the Commonwealth Forces who died during the two World Wars.
For purposes of commemoration the dates are as follows:
4 August 1914 to 31 August 1921
3 September 1939 to 31 December 1947
I hope that the information is useful.