JSFiddle - React, Tailwind, and code Playground

JavaScript

const items=[{name: '1',date: '10 dec'},{name: '2',date: '10 dec'},{name: '3',date: '11 dec' }];

const dates = items.map(item=> item.date)
const datesNoDupe = Array.from(new Set(dates));

const output = datesNoDupe.map(date=>{
  return items.filter(item=>{
    return item.date === date;
  });
})

console.log(output)