Save your calendars: this is a project for the most astute recycler. Every 28 years the calendar repeats itself. 2024 will look exactly like 1996, down to the day.

Our calendar isn't exact. With respect to the way we revolve around the sun, there's actually 365.253 days in a year. This, of course, leads to a leap year every four times around to make up the difference. And then there's the fine tuning -- to make up for the 0.003 of a day left over, there's another extra day added every 400 years.

Recycling, like problems with waste and garbage have been consistent issues through our entire history. They're even older than the Julian Calendar.

When people started living in fixed settlements they had to think seriously about their garbage problems. Before the growth of cities, it wasn't as bad. Nomadic life was the norm. If garbage did pile up or get a little annoying, you could pick up and move away from it.

In ancient Troy, the city literally rose above its own garbage. Charles Gunnerson has calculated that the elevation of the city rose 4.7 feet per century due to debris accumulation. If all the garbage produced in Manhattan were left in place, Gunnerson estimates that the elevation of this modern city would increase at almost the same rate as Troy, circa 2000 B.C.

It's interesting to note that one of the first municipal dumps in the western world was established as early as 400 B.C. on the outskirts of Athens. All citizens were required to bring their own trash a mile past the city's walls.

Back in 1200 A.D., the Maya were doing something which looked a lot like what we, today, would call source reduction. They were dealing with shortages of raw materials by stopping waste at its roots. Archaeologists have discovered that during this period, the Mayan practice of burying the dead with all their worldly possessions was discontinued. It is believed that this was in direct response to shortages of materials for making pottery and jewelry.

You shouldn't be surprised to see waste reduction measures being instituted over 700 years ago. Our current excitement about recycling is nothing new.

Now, like for the Maya, some natural resources are in dwindling supplies. But with a growing world population and the development of industries and products which pollute the environment, our concerns are even bigger.

Over only about the last 150 years, our world has changed immensely. Before 1850, most paper was made from recycled rags, not wood pulp. In 1908, the Model T was introduced. And in 1936, the first paper milk cartons appeared on grocery store shelves. About the same time, Nylon and other plastic materials were being developed. All of these relatively recent developments have changed how we live and how we consume.

The calendar keeps going around. As with those who came before us, we're at a time in our history when we need to think clearly about how to deal with our waste.