JSFiddle - React, Tailwind, and code Playground

JavaScript

var arr = [1367848800000, 1367935200000, 1368021600000,
           1368108000000, 1368194400000, 1368367200000,
           1368540000000, 1368626400000, 1368712800000],
    i = 0,
    result = arr.reduce(function(stack, b) {
        var cur = stack[i],
            a = cur ? cur[cur.length-1] : 0;

        if (b - a > 86400000) {
            i++;
        }

        if (!stack[i])
            stack[i] = [];

        stack[i].push(b);

        return stack;
    }, []);

console.log(result);