While this approach is certainly an alternative to mine, it does not help with the core problem, which is the DCI Data Recalculation:
Unfortunately, you cannot pass a timestamp parameter the functions PushDCIData, which could define where to put the new value in the DCI table. Therefore, it will always put the new value to the actual current timestamp.
When looking at the sourcecode, I would see the following location, at which this problem could be addressed:
In line 114 of src/server/core/dci_recalc.cpp, the recalculateValue(value) function is called, which calls the function transform(value, elapsedTime) in line 2151 of src/server/core/dcitem.cpp.
In this function, in line 999 of the same file (dcitem.cpp), a ScriptVMHandle object is created, using the function CreateServerScriptVM(...). This function CreateServerScriptVM(...) could have an optional timestamp parameter, which would tell the script VM to simulate an execution at the given point in time, defined by the given parameter.
The value for this timestamp parameter could be extracted from the ItemValue &value (which is the current DCI value to be recalculated) of the calling function, using value.getTimeStamp().
This approach, however, would require refactoring the implementation of NXSL functions, like time(), GetDCIValue(...) or GetDCIRawValue(...) as their behavior should then be adapted, accordingly.
(I'm sorry, if I have some weird ideas, which might sound reasonable to me but not for others ;D)
