What is the source of your 2 data tables? 2 sheets in the same excel workbook? 2 tables in the same SQL data base? 2 Tableau published data sources? The reason I ask is before tackling your date issue, I want to understand whether you can 'join' your data or have to 'blend'. With Tableau blends, you have a primary & secondary data source and your data will only ever contain a row for the information in your primary data source, so you may not get everything you expect.
For example, I notice in your sample data above that your 1st 'ride information' table has data for 4 drivers, only 1 of which exists in your session data table (and there are drivers in there which aren't in the ride information). If you're expecting an output of 1 row for the 6 different driver IDs I can see in your sample data, then a Tableau blend is unlikely to work without a further data source set up containing 1 row per driver per date (which will need maintaining, so not ideal).
To further help, the following would also be useful:
1) An example of what you expect the actual output to be given the sample data you've provided above
2) Would either of the tables contain multiple rows for a driver - you've given a very narrow sample.. I'm assuming the ride information could have multiple rows for the same driver on the same date but with different times; I'm unsure about the session data
3) The ideal would be to post a packaged workbook with a good sample of the data you're working with (see Packaged workbooks: when, why, how for further info on why this is useful)
4) The version of Tableau you're working with.