The reason for the problem may be incompatible browser issues.
solution:
1. Locate the file ext-all.css in the framework EXTJS
.x-date-picker{border:1px solid #1b376c;border-top:0 none;background:#fff;position:relative;}属性。
( Can + F to quickly find the file in ext-all.css search .x-date-picker keywords with Ctrl )
2. Then add at its rear width: 185px;
即:.x-date-picker{border:1px solid #1b376c;border-top:0 none;background:#fff;position:relative;width: 185px;}
3. Restart the project can be.
PS: I own directory provides ext-all.css of: extjs / resources / css / ext-all.css