Regular expression on the Created date does not work.

Problem/Motivation

A filter on the field "Webform submission: Created" exposed as a regular expression does not work.

Steps to reproduce

1) Create a webform;
2) Add some fields and a "date list" field called for example birthday.
3) Create a view on the submissions.
4) Expose filter on both the "birthday" field (mentioned in step 2 above) and on the "Webform submission: Created" which is the date when the webform was submitted. Expose these filters as regular expressions.
5) The regular expression works for the "birthday" field but does not work for the "Webform submission: Created" field.