I tried updating the cube once sometime last year and I need to know the date I did that? Is it possible to see that in the status tab in Cognos 10 administration?
If your cube is published to Cognos BI then you can easily access cube metadata using Report Expressions in Report Studio:
Edit the Report Expression and use one of the cube report functions, dragging in the dimension as the parameter:
CubeDataUpdatedOn([CubeName].[DimName])
Run the report and it will give you the date on which the source cube was updated.