cron schedule, celery heart beat scheduling

 https://stackoverflow.com/questions/60136460/run-celery-task-for-specific-time-period

I suppose you're using Celery beat to run periodic tasks. Your requirement should be possible using Crontab schedule. Specifically following this example that's given there:

crontab(minute=0, hour='*/3,8-17')

Execute every hour divisible by 3, and every hour during office hours (8am-5pm).