src/DataService/DataService.php
public function isValidTimeStamp($timestamp)
    {
        return ((string)(int)$timestamp === $timestamp) && ($timestamp <= PHP_INT_MAX) && ($timestamp >= ~PHP_INT_MAX);
    }
public function isValidTimeStamp($timestamp)
    {
        return ((string)(int)$timestamp === $timestamp) && ($timestamp <= PHP_INT_MAX) && ($timestamp >= ~PHP_INT_MAX);
    }
Checks if input string is a valid timestamp or not
@param string timestamp contains input timestamp-like string
@return bool