Additional Math Pages & Resources

Tuesday, February 22, 2011

How Long Has It Been? Part I

Time is a word we use to describe our movements through time. Wait. That won't work as a definition. What is time anyway? A definition of time might include: 

  • a non-spatial continuum in which events occur in apparently irreversible succession from the past through the present to the future
  • a system of sequential relationships between events
  • a means by which we sense and record changes in our environment and in the universe
  • a way to describe separation among events taking place in the same location
  • a measured duration of activities 
  • a fourth dimension
There are other ways to define time but these are adequate for our purposes today. If you have more "time" then you can go read these other Excel Math blogs on time: CalendarsDaylight savings.   Elapsed Time.   Avoid Being LateThanksgiving MathOnce in a blue moon.

Math class is when our schools teach reading, measuring and recording time (watches and clocks and calendars), while History is where you learn about events that happen and their long-term meaning.

Today I want to think about the progression of time and how we keep track of things that have happened and may eventually happen. While we are cruising along in time, how do we maintain awareness of where we are in the stream, where we are going, and where we have been?

We use a mental ability called our memory, a skill that enables us to retain, recall and relive events.

We might use an anniversary. When a special date comes around each year, we think back to the day (and year) we were born, married, enlisted, graduated or retired. At the end of a person's life we have memorial services to refresh our memories about significant things they did or said.

Many people use calendars (in paper or electronic form) to keep track of the passage of days and weeks, the events we have planned in the future, and the activities of the past. Here's a calendar for the month of January that my wife has saved from a decade ago.


In Excel Math we teach kids about units of time, using a calendar, and calculating the day of the week or month "... so many days or weeks in the future (or past)." Why bother with this?

Here are some examples of how you use time as a grown-up person:

1. You have make an appointment to take your driving test on a business day at least 6 weeks before your birthday. Your birthday is the 21st of June 2011. What is the last day you can make this appointment?

2. If you owe income tax, it may be deferred for a period not to exceed 180 days after you are discharged from military service. If you pay the income tax in full by the end of the deferral period, you will not be charged interest or a penalty for that period, if you remembered to notify the IRS before your service impacted your ability to pay.

If you do not notify the IRS in advance, you will owe interest on any tax not paid by April 15, even if you should qualify for the 2-month extension because you were out of the country. The interest runs until you pay the tax; even if you had a good reason for not paying on time, you will still owe interest.

A late filing penalty may also be charged. The penalty is 5% of the amount due for each month (or part of a month) your return is late. The maximum penalty is 25%. If your tax return is more than 60 days late, the minimum penalty is $135 or the tax amount, whichever is smaller. You might not owe the penalty if you have a reasonable explanation for filing late. 

The Federal Government and the IRS do not consider "I didn't remember the date"  or "I couldn't figure out how many months I was gone" as reasonable explanations! If you have suddenly remembered that this example is going to apply to you this year, here's the form. Just change the date to tax year 2010.