<?php

$count = 25000;
$functions = [
    'carbon' => function ($i) {
        return now()->subDays($i)->format('Y-m-d');
    },
    'strtotime' => function ($i) {
        return date('Y-m-d', strtotime("$i days ago"));
    },
    'timestamps' => function ($i) {
        return date('Y-m-d', time() - ($i * 24 * 60 * 60));
    }
];

$results = [];
foreach ($functions as $key => $func) {

    $time = microtime(true);

    for ($i = 0; $i < $count; $i++) {
        $date = $func($i);
        echo $date . PHP_EOL;
    }

    $time = round(microtime(true) - $time, 6);

    $results[$key] = $time;
}

foreach ($results as $key => $time) {
    echo 'Parsed ' . number_format($count, 0, ',', '.') . " dates in $time seconds using $key.\n";
}