system/CodeIgniter.php
public function initialize()
	{
		// Set default timezone on the server
		date_default_timezone_set($this->config->appTimezone ?? 'UTC');

		// Setup Exception Handling
		Services::exceptions()
				->initialize();

		$this->detectEnvironment();
		$this->bootstrapEnvironment();

		if (CI_DEBUG)
		{
			require_once SYSTEMPATH . 'ThirdParty/Kint/kint.php';
		}
	}
public function initialize()
	{
		// Set default timezone on the server
		date_default_timezone_set($this->config->appTimezone ?? 'UTC');

		// Setup Exception Handling
		Services::exceptions()
				->initialize();

		$this->detectEnvironment();
		$this->bootstrapEnvironment();

		if (CI_DEBUG)
		{
			require_once SYSTEMPATH . 'ThirdParty/Kint/kint.php';
		}
	}
Handles some basic app and environment setup.