How to show results for half an hour in timeHeaders

I try set timeHeader in javascript

timeHeaders: [
{ groupBy: "Day",format : "dd/MM/yyyy" },
{ groupBy: "Hour", format: "HH:mm" },
],

I need to show the half an hour but i try add the code it make hard loading and reload long time because 1 cell show 60 minute.
{ groupBy: "Minute", format: "mm" },

What are some ways I can add a half hour show in timeHeaders. Please help me