Do you need an easy-to-use system for creating calendars? The free Perpetual Calendar by Vertex42.com is one of the most powerful and flexible calendar tools available, and all you need is Microsoft Excel. You can start the calendar with any month of the year, so if you start your plan mid-year or you need a convenient school calendar, this template will work well. In addition to letting you create printable yearly and monthly calendars, you can keep track of recurring yearly events such as birthdays, anniversaries and holidays. You can add these events to the "Year" worksheet and up to 3 events per day will automatically be added to the 12 individual monthly calendars (located on the 12 numbered worksheet tabs). If you use formulas like the examples provided, when you change the year the calendar will automatically include your events in the monthly calendars (that is why this calendar is "perpetual"). More information about how to use the Perpetual Calendar spreadsheet, such as how to add the event formulas or create a PDF, can be found on the official author page.