This demo shows how you can have both of the axis on an XY chart be date-based.
This is achieved by setting their type parameter to "date".
Furthermore, you'll notice that while X (horizontal) axis is daily, the Y (vertical) axis displays it in time. The setting which allows to set granularity for each axis individually is minPeriod.
For a version of this chart with a regular value-based Y axis, check this demo.