If you have configured your Calendar control to display both date and time, and you enter only the time into the Calendar control's textbox, the control will automatically add the current date to the time you have entered when you focus away from the control.
However, at times users noticed that the Calendar control fills in an older date, and not the current date. For example, if today is 10 October 2018, after filling in the time in the control's textbox, then clicking away, the Calendar control fills in 09 October 2018 instead of 10 October 2018.
This has been acknowledged as a bug to be addressed in a future version of K2.
The workaround is to advice users NOT to fill in the time into the textbox, and let the Calendar control fill in the date. Use the calendar in the Calendar control to pick the correct date and time.