The Forecast interface allows users to view a forecast of when the job will run, based on the current scheduling rules defined for the job. The days that the job will run are marked in green.
It should be rare, but if you see a day marked in red, it means that it is a scheduled date in the past. This only happens if the job is behind schedule, typically due to JobServer being shutdown.
The only rules that are not included when viewing the calendar, are dependency rules. This is because dependency rules are typically dynamic, and viewing a schedule forecast with the dependency rules included would be confusing to the user and not informative in most cases.
If you select the "Show Date/Time Details" checkbox, you will see the specific dates and times of when the job is forecast to run, displayed in a list. This is useful when you want to see the specific time of day a job is to run on and also when a job runs multiple times in one day.