Here I have used your sample data which you have given in your question.
Please see first below screens shot of Data.
Now I have used this data in Tableau.
In Tableau, I have used wildcard filter where I have used condition to select all value which contains / .
And you can see in the above Tableau worksheet that only date value is there.
You don't need to create any calculated field.
Please let me know if you have more question on this.
Please mark correct and Helpful if it works for you
when you will import data in tableau then you will find the field is string format just change the field to date and time. it will work as per your requirment.
Please see below. if it does not help so i would like to see your workbook with dummy data.
DAte format change.twbx 37.8 KB
You can create a calculated field as,
and pull this in the filter section excluding NULL.
I have attached the workbook for your reference.
datefilter.twbx 14.6 KB