I'm working with two sets of WW2 meteorological charts and I'd appreciate advice as to what the abbreviations for the time datum mean. One, which is a published Daily Weather Report with observations for a large number of continental stations and maps for four times throughout the day, carries the legend "Alle Zeitangaben in DGZ". It's the DGZ that foxes me; I assume the D = Deutsches and the Z = Zeit, but what's the G?

The other version is used on a set of working charts on which the time is given as DSZ; again I'm confident the D and Z are Deutsches and Zeit, but what is the 'S'?

Any advice would be appreciated.

Brian