Backup file names.

I created a backup cron manually so:
0 0 1,11,21 * * root /usr/local/CyberCP/bin/python /usr/local/CyberCP/plogical/backupScheduleLocal.py

So in backup folder:
backup-domain.com-11.30.2020_21-07-40.tar.gz
File Created Date: 1.12.2020 [Day-Month-Year]

So why is created date and date in filename is different? Should not be both dates are some?