Logs are getting auto deleted after the date is changed.

Bug report

Bug description:

I have written a code that would rotate logs on midnight maintaing backup of 1 day. But the next day, the previous logs are getting deleted.

For example :
While I am checking logs on 14th Feb, I noticed that all the logs generated on 13th Feb, got deleted from instancelogs.log.2025-02-13. The first log generated on 14th Feb is getting stored in instancelogs.log.2025-02-13 file instead of instancelogs.log file , the remaining logs for 14th Feb are correctly stored in instancelogs.log file.

Please look into the issue as we are losing all the logs for 13th of Feb.

I am using below code to handle logs:

import logging
from logging.handlers import TimedRotatingFileHandler


#logger instances for PPT creator
LOG_FILE_PATH = "../STORE_LOGS/instancelogs.log"

instance_logger = logging.getLogger('instance_logger')

instance_logger_file_handler = None


instance_logger_file_handler = TimedRotatingFileHandler(LOG_FILE_PATH, when='midnight', interval=1, backupCount=1)
instance_logger_file_formatter = logging.Formatter(
    fmt="[%(asctime)s] - [%(levelname)s]  - [%(filename)s] - [%(funcName)s] - %(message)s",
    datefmt="%d-%m-%y %H:%M:%S")
instance_logger_file_handler.setFormatter(instance_logger_file_formatter)

instance_logger.setLevel(logging.DEBUG)
instance_logger.addHandler(instance_logger_file_handler)

CPython versions tested on:

3.9

Operating systems tested on:

Linux

从 Python logging.handlers.TimedRotatingFileHandler 的实现及其 rollover 行为入手，使用提供的午夜配置作为复现用例。检查午夜之后的第一条记录如何被分配到轮转后的文件名，以及 backupCount=1 如何删除文件。当此前一天的日志保持完整，且新一天的记录写入活动日志文件，并为此用例提供回归覆盖时，即表示完成。