Python TimedRotatingFileHandler how does rotation happen

So, after reading documentation and couple of stackoverflow questions and trying it in Python 3.4 i dont get it. When does it rotate and on what conditions?

There are 2 threads, they never stop. They call this code (i know that logger is a singleton already, there's more unrelated code in Utility):

import logging
from singleton import Singleton
from logging.handlers import TimedRotatingFileHandler

class Utility(metaclass=Singleton):

    def _logger(self):
        logger = logging.getLogger("main")
        logger.setLevel(logging.INFO)
        if not logger.hasHandlers():
            handler = TimedRotatingFileHandler(
                filename = "info.log",
                when = 's',
                interval = 10,
                backupCount = 10,
                encoding = 'utf-8'
            )
            logger.addHandler(handler)
        return logger

    def log(self, *text):
        self._logger().info(' '.join(str(t) for t in text))

Revisiting old question, just use loguru