Looks like we can't reproduce the issue or there's a problem in the test case provided.
min/max date problem
Add date component to form, set min date value, max date value to date picker of date field: field.getDatePicker().setMinDate(value).
Open date selector - dates before min date and after max date are grayed. move to next month or year(this is to do all date picker grayed). Return back to previous value(to see min and max date)
Result - date picker is disabled, even between min and max date.
I believe this has been fixed as part of http://www.sencha.com/forum/showthread.php?205930 in 3.0.2. You can confirm that it works in 3.0.5 by visiting http://qa.sencha.com:8080/examples-3...ace:filtergrid and opening the Last Updated column menu, and using the date pickers in that menu.
In the future, please provide a test case that demonstrates the issue - we have the bug template for a reason.