Steps to Reproduce

http://zkfiddle.org/sample/3vkuate/4-datebox-problem-format-problem
open the popup select a day

Current Result

the time changes when selecting a day
updates to the time are ignored
sometimes the day jumps to a day +1 of the selected date

Expected Result

keep the time and date as selected

Workaround

adding space in the date format between 'a' and 'hh' doesn't have the problem

'yyyy-MM-dd ahh:mm' -> problem

'yyyy-MM-dd a hh:mm' -> no problem