Data Sense, which was introduced with the GDR2 update (aka Update 2), allows you to track your data usage over time. With it, you can...
- Track data using for individual app over mobile and wifi connections
- Set a usage limit (unlimited, one time or monthly)
- Restrict background data usage when near your data limit
- Use the Data Sense service to reduce data usage when browsing (opt-in)
Usage for a single day
The easiest way to monitor data usage for a single day is to...
- Go into Data Sense app
- Select Settings then Set Limit, select Monthly
- Now set today as the 'Monthly reset date', then tap Done
When you view the Overview or Usage pivots, you should see the data usage for that day only.
Note: changing these settings does not delete previous data. You can try out the above, then undo the changes with out erasing the previous data usage.