This type defines a callback function to calculate and return the time parameter offsets from a calendar time object in GMT.
Syntax
 #include <prtime.h> 
 typedef PRTimeParameters (PR_CALLBACK_DECL *PRTimeParamFn) 
    (const PRExplodedTime *gmt); 
Description
The type PRTimeParamFn represents a callback function that, when given a time instant in GMT, returns the time zone information (offset from GMT and DST offset) at that time instant.