Job role Start Date changes by itself to previous in case changing start date + 1 day

Preconditions:
I found HR Admin user with such Email: civihr_admin@compucorp.co.uk and perfomed tests with it.
His contract have dates 25/08/2016 - 05/09/2016

1. Go to Job Roles
2. Click Add new Job Role
3. Enter some title and choose contract from preconditions
4. Click Save new Role
5. Click Edit
6. Change Start Date to 2*6*/08/2016 and click Save
Expected Result: Data will saved as 2*6*/08/2016
Actual Result: Data changes to 2*5*/08/2016 by itself