The labels of the buttons in the Datepicker can be configured. Please provide the same option for the Timepicker.
For simple changing label of done button, please change it's text. Head into /pro/time-picker/timepicker.component.html and search for line 60. There you can change text of this button.
But if you need option that allows you to translate label of button to other languages (for example german, spanish, french, polish, etc), we have to write it.
PS: If you need only simple input, which allows you to change label of the button while you don't want to edit our source files, we will release it in our next update.
Please let me know one more time, what exactly do you need.