I'm looking at a Data Warehouse which collections data from systems across the world. The Data Warehouse uses UTC for time but only stores the UTC offset and not the timezone. I have noticed that the datetime data from e.g. America has been inserted with an offset of +0000 which suggests it has been stored as UTC instead of local time. As far as I can see in the code that loads the data there is no conversion to convert the datetime from local time to UTC.
I'm fairly new to DWH data modelling but from what I have read I would have thought that we should either store the data with the converted UTC offset, store the datetime with timezone included or store UTC and local datetime as this could have an impact on reporting. None of the reporting teams have raised an issue with this at the moment so should it be a concern or is it acceptable to save everything as UTC when the data is coming in from different countries across the world?