[FIX] date and datetime field in form edit mode is too short for Chinese

![_006](https://cloud.githubusercontent.com/assets/275267/3341579/b0c6144e-f889-11e3-9ba2-121e1811718d.png)
![_007](https://cloud.githubusercontent.com/assets/275267/3341581/b6bb432e-f889-11e3-9ebc-86a1fd259549.png)
In Chinese, It look like this.