You can use a parameter to get the selected date in the microflow you need as long as the microflow is being triggered (on change, or from a button f.e.) from within the data view of the entity that contains the date attribute.
I usually achieve this by creating non persistable entity and with DateTime attribute I can send information to page. This is when I don’t want to store DateTime in Database tables.
So the point is you can send page parameter to page via entity.
Otherwise if it is calculated datetime, then you can use what Prashant Singh suggested by using dataview and setting datasource as microflow (still you will need to have entity).
Use the datepicker on a datetime attribute of an entity.
In the homepage use dataview and set datasource as microflow to get the object, inside that dataview use the datepicker and set an OnChange event in the properties of the widget to call a microflow.
You will get the object as a parameter in the microflow and you can make use of the date value.