Run results for: create a specific Date object vs modifying an existing one

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/26.5 Safari/605.1.15

Browser: Safari 26

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: 2 months ago

setTime

841.6M/s

parse Date

125.3M/s

new Date

46.5M/s

modify Date

6.4M/s

View exact numbers

Test name	Executions per second
✓ setTime	841,633,344 Ops/sec
parse Date	125,337,448 Ops/sec
new Date	46,548,308 Ops/sec
modify Date	6,361,326 Ops/sec

HTML Preparation code:

<div id="date.create"></div>
<div id="date.set"></div>
<div id="date.setTime"></div>

Script Preparation code:

var create;
var elCreate = document.getElementById('date.create');

var set = new Date(0);
var elSet = document.getElementById('date.set');

var time = new Date(1999, 1, 28).getTime();
var setTime = new Date(0);
var elSetTime = document.getElementById('date.setTime');

Tests:

new Date
create = new Date(1999, 1, 28); elCreate.innerText = create;
modify Date
set.setDate(1); set.setFullYear(1999); set.setMonth(1); set.setDate(28); set.setHours(0); set.setMinutes(0); set.setSeconds(0); set.setMilliseconds(0); elSet.innerText = set;
setTime
setTime.setTime(time); elSetTime.innerText = setTime;

Run results for: create a specific Date object vs modifying an existing one

How expensive is creation of a Date instance.

new Date

modify Date

setTime