The calendar displays a schedule of when jobs are set to execute, including cron jobs which are not executed immediately, but are instead scheduled and often repeated weekly. The executed jobs are displayed in gray.
If you need to pause job execution for a particular day due to maintenance or other reasons, you can avoid deactivating the jobs one by one. Instead, you can simply select the time period in which you don't want the jobs to run by holding down on a field. This way, you can block the jobs without having to deactivate and then reactivate them later, or manually stopping each job for the day.