BusyCal is a useful and powerful calendar app for working with events and to dos. The app works with iCloud, Google Calendar, Exchange, Office 365 and other CalDAV Servers. This helps with coordinating and syncing all the various calendars you may have into one place.
There are different calendar views and you can even see the upcoming weather. You can use pinch gestures to zoom in and out of weeks.
To Do items are also displayed in the calendar and will remain until completed. You can sort the items in various ways like date, priority, calendar, etc. The app can even sync with Reminders on your iOS or Mac.
If you need help with the app, check out the help page.
All kinds of personalization is available to make this app a nice way to unify all your different schedules into one place. Your productivity can be greatly improved using BusyCal.