src/Uploadcare/Api.php
public static function dateTimeString($datetime)
    {
        if ($datetime === null) {
            return null;
        }

        if (is_object($datetime) && !($datetime instanceof \DateTime)) {
            throw new \Exception('Only \DateTime objects allowed');
        }

        if (is_string($datetime)) {
            $datetime = new \DateTime($datetime);
        }

        return $datetime->format("Y-m-d\TH:i:s.uP");
    }
public static function dateTimeString($datetime)
    {
        if ($datetime === null) {
            return null;
        }

        if (is_object($datetime) && !($datetime instanceof \DateTime)) {
            throw new \Exception('Only \DateTime objects allowed');
        }

        if (is_string($datetime)) {
            $datetime = new \DateTime($datetime);
        }

        return $datetime->format("Y-m-d\TH:i:s.uP");
    }
Convert datetime from string or \DateTime object to ATOM string

@param string|\DateTime $datetime
@throws \Exception
@return null|string