How do calendars help with time management?

If you want to plan what work you will carry out and when, and if you have to make sure this is done in a certain timeline, as well as allow time for holidays and visits to family and friends, then a calendar makes this all possible.

You can see how much can be done in any given month, allow for public holidays when you won't be able to access certain businesses, like banks, and plan the time needed to travel or to prepare for the work you have scheduled within a certain week or longer. You can see at a glance which periods are busiest and where it will be difficult to fit something new in.