Silence PHP errors related to date_default_timezone_get()

**Before**

![before_requirements](https://cloud.githubusercontent.com/assets/73419/5121524/4a29434a-7094-11e4-9dfb-3b895a58e8d3.png)

**After**

![after_requirements](https://cloud.githubusercontent.com/assets/73419/5121525/4c97b53a-7094-11e4-8e2a-533d9174d2ac.png)