I want to select the date from the calendar and save it. However, I cannot select the date. Could you possibly give me some advice ?
You cannot have editable fields in a template grid.
Use listview incase you want to have editable data. Also when using list view, use a datepicker widget instead of text incase you want to edit the date.
Few things that I notice
You can select the date but may be due to the custom styling it is not easily seen on screen for the user.
Your save button is out of context of the template grid – so you will not be able to get hold of the current object selected to save it or to do some processing. Move the button to the template grid control bar if you want to access the selected object.
Otherwise look at what Shreyash has already mentioned and see if that suits your use case better.