Are you ever expecting storing anything but dates in your field? If not, consider changing the data type to "Date (date)" instread of "Text (string)" - then it will just work correctly like you expect.
If not, you can add a rule to your field:
Condition: field contains "T"
Action: Set field's value to:substring-before(., "T")
However this is hacky so I would advise just changing the data type instead.
Note: for testing purposes, it's often useful to also drag the same field into the view as a plain textbox. Then you can see and debug the value right away without the need to save.
David Airapetyan / Software Services ArchitectQdabra® Software / Streamline data gathering to turn process into knowledge