You maintain a sales model with a large Sales fact table (80 million rows) and several dimension tables. A colleague added a new measure that must return the running count of distinct customers using the DISTINCTCOUNT function. Performance is acceptable, but you notice the Sales table stores a full DateTime column for OrderDateTime, and the model size is much larger than expected. Reporting only needs analysis at the day level, and a separate Date dimension already exists marked as a date table. Which single change will most effectively reduce the Sales table's storage footprint?