I experience hard time to focus the field using iPhone 6.
First in my project, than in your demo http://demos.telerik.com/kendo-ui/datetimepicker/index
After multiple tests, I found how to get it done, but It's not UX friendly.
Tap and hold on the field until the label get selected.
Than tap under the selected zone to get the focus in the field.
iOS 8.4.1
Safari
Thank you