It's Just a Matter of Time

From Year to Year

In general, New Year’s Day is one day later in the week than it was in the year before. Sometimes, it is two days later.

1. Why does this happen? Think about the following:
   • the number of days in a week
   • the number of days in a year
   • the number of days in a leap year

2. People say that a year is made of 52 weeks. Is that precise?
3. How do you know if a year is a leap year?

From Month to Month

Complete the table with the total number of days in each month for the current year.

1. How many months have 31 days?
2. How many months have a total of 30 days?
3. How many months have a total of 28 days?
4. Why is it necessary to clarify the question for 30 and 28 days?
5. From a previous Family Math Activity, you may remember that January and February were added to the beginning of the calendar when people changed from the Roman calendar to the Julian calendar, and later to the Gregorian calendar in an effort to have the calendar more closely match the seasons.

   If you disregard January and February in your table, do you see a pattern in the number of days in a month for the remaining 10 months? How would you describe it?

   MAR	APR	MAY	JUN	JUL	AUG	SEP	OCT	NOV	DEC

From Day to Day

Dividing time into weeks and months makes it easy to keep track of special days during the year.

Imagine if you had to remember that spring begins on day 80, summer begins on day 172, autumn begins on day 266, and winter begins on day 355. You would also need to remember that if it is a leap year, the seasons start on days 81, 173, 267, and 356.

On which day of the year do some of the special days in your life occur?

These tables can help you answer the question. The numbers indicate how many days of the year have passed before the month starts. Add the number given for the month and the date in the month of the event.

Non-leap year:

Leap year:

Examples:

• Valentine’s Day (Feb 14) is the 45th day of the year, whether or not it is a leap year. (31 + 14 = 45)
• Independence Day is either the 185th or the 186th day of the year, depending on whether it is a leap year. (181 + 4 = 185 or 182 + 4 = 186)

A Perpetual Calendar

Months may start on different days of the week, but there is a fixed pattern in the way the days of the month appear in the columns of a calendar. The 8th day of the month is always the same day of the week as the 1st, the 9th is always the same day of the week as the 2nd, and so on.

You can create a perpetual calendar—one that can be used with any month in any year.

This layout will work for any month when used with the frame or overlays below.

These covers can be folded and used at each end of the table to cover the extra days.