What did you do to cause this?
What page were you on? http://path.to.traq/myproject/settings/milestones
What PHP and MariaDB versions do you run? PHP version 5.3.23, MySQL version 5.5.27-cll. Oooh, I thought that that was a reporter who replaced MySQL with MariaDB. I wish I could have it, though: it is lovely!
Describe the defect: When you edit a milestone, it seems that something like 2000-01-01 is added in the Expected field. I've not investigated it more ghoroughly, though.