http://forum.zkoss.org/question/90132/wrong-behaviour-of-datebox-when-overwriting-time/

The „Date and Time Picker" (datebox) has a very strange behaviour when trying to modify the time (in 24-hour mode).

It can be reproduced on http://www.zkoss.org/zkdemo/input/date_and_time_picker (http://www.zkoss.org/zkdemo/input/dateandtime_picker) in the field "Long and Medium" as follows:

Click on the calendar symbol in the datebox.
Modify the time to anything between 04:00:00 and 09:59:59 or anything between 14:00:00 and 19:59:59.
Hit enter.
Click on the calendar symbol in the datebox again.
Mark the entire time expression.
Hit the "2".
It appears "02".

I noticed this when I wanted to enter 23:59:59 but instead got 02:35:09.

Additional info:
The same behavior under ie10 and current Firefox.
This issue is not only on the demo side it occures also on my application.