New Year’s Eve. It’s the end of another year and the beginning of the next. It is the end of one fixed period of time, the end of one more revolution of the earth around the sun. The end of a year is a "significant moment." We are crossing a boundary, shedding the old year as a snake sheds its skin, leaping into something new and young and different, something full of risks and peril, something full of hope and promise.

We call the first month of the year January, after the Roman god Janus, the two-faced god who looks both backwards and forwards into time. Janus presides over thresholds. At the new year, we look back over the country of the past, look back and evaluate where we are and where we came from. We note the hills and valleys of good and bad fortune. We remember the dead ends or the green pastures. But we cannot go back; the path goes only in one direction. Thus, we turn our gaze over the threshold and toward the country of the future. We assess the lay of the land. We attempt to draw a map. We make our "New Year’s resolutions," and to plan for better days.

Yet we are just in time. The boundary is not really real; it is a boundary that humans have created for their own convenience. Humans create the meaning; humans give the significance.

The calendar is a human invention with a long history. Five thousand years ago, the Sumerians, watching the movements of the sun, moon, and stars, first divided the year into 30-day months. (Our word "month" is related to the word "moon.") The Egyptians invented the 365-day year, and, in 46 BCE, Julius Caesar reformed the calendar by adding in the leap year, the year with an extra day, to keep our calendars in line with the heavens. But even his calendar was off by 11 minutes, 13.5 seconds. This discrepancy added up over the centuries so that by the 16th century the calendar was about 10 days behind the sun and stars. As a result, Pope Gregory XIII, in 1582, with the stroke of a pen deleted ten days from the calendar. The calendars of Catholic countries were, thus, immediately brought in line with the heavens. Protestants, of course, had some problem with getting directions from a pope. England, for example, didn’t adopt "new style" until 1752. The "new style" is the Gregorian calendar, which we still use to this day.

And the calendar is just one man-made marker of time. We have invented many more: the hour, the minute, the second, which, since 1967, we have now defined as equal to 9,192,631,770 oscillations of the cesium atom’s resonant frequency.

The story of the hour is particularly interesting. With the invention of the sundial, the day was divided into smaller, regular units. In the northern hemisphere, however, the length of those hours varied according to the season. The daylight hours were shorter in the winter and longer in the summer. The reverse was true for the night hours. The sons of St. Benedict, the monks, were particularly keen on keeping track of the hours because they were pledged to pray at regular intervals of the day. The canonical hours were the hours for specified prayers: matins, lauds, prime, terce, sext, none, vespers, and compline. Using water clocks and specially marked candles, the monks were particularly ingenious about keeping hours both during the day and during the night. An interesting footnote: The word "none" is literally the Latin word for the ninth hour, but over the course of the Middle Ages, the prayers of the ninth hour were shifted to mid-day. Hence, our word "noon" which signifies not 9 o’clock but 12.

The calculating of time encountered a major revolution in the 14th century, when the mechanical clock was invented. Suddenly, the length of the hours was no longer dependent on the movement of the sun. 24 equal hours replaced the 24 unequal hours of earlier times. Originally, clocks without faces were attached to bells, which rang out the hours from city squares. Our word "clock" as well as the German "Glocke" come from an earlier Indo-European cognate meaning "bell." The French word "cloche" still means bell. Later, when faces were added, clocks became sources of civic pride, with progressive cities being the first in their region to have a town clock. An invisible web of marked time immediately descended over city life. Differences in the experience of time became an essential distinction between urban and rural life. In the country, the life of peasants was still governed by the natural rhythms of sun and seasons. In the cities, however, work time was now measured by the clock. As clocks became smaller and portable, this distinction became less dramatic.

Since the 14th century, we all swim in the ocean of the clock’s hours, minutes, and seconds, yet none of us can define adequately what time is. Einstein, for example, said that time is whatever is measured by a clock. This is certainly a practical solution to the problem but hardly one that would satisfy a philosopher. In one of the most famous attempts to define time, St. Augustine struggled to analyze its metaphysical reality. "What is time," he wrote, "If no one asks me I know. If I want to explain it to someone who does ask me, I do not know." But he does know that if nothing were passing away, there would be no time. Time, however, cannot exist in the past, for the past has already ceased to be. Similarly, time cannot exist in the future because the future has not yet come to be. Time can only exist in the present, but how long is that? If you point to the present hour, I can reply that approximately 45 minutes are already in the past (and, hence, non-existent) and approximately 15 minutes are in the future (and, hence, non-existent). Similar observations can be made for the present minute and even the present second. The "present," then, seems to be a string of infinitely small units of time. By the time you grasp one unit, it has already flitted, like a butterfly into non-existent past. The present moment arrives and departs "just in time."

But it is not satisfying to say that both the past and future do not exist in any sense of the term, even St. Augustine realized that. He argued that there is a "past" that lives in the present. There is a past that lives in our memories. And he could have added that there is a past that lives in material artifacts. Fossils, manuscripts, clay pots, cathedrals, statues, and yesterday’s newspaper all live in the present of things past. These are the true keys of memory, and they unlock the vault of the past.

Benjamin Franklin wrote that "time is money." Well, time certainly shares some attributes of money. Those attributes of time are enshrined in our language. We "spend" time at work, and we "save" time by avoiding time-consuming activities. We can also "waste" time by passing the day in idle activities. We can be generous with our time or selfish. We can live on "borrowed" time, and we can also "sell" our time to the highest bidder. Time, our language suggests, is indeed filled with value, and it has value, at least in part, because our personal supplies are limited. We all live with the specter of death just over the horizon. As Seneca writes, we are dying daily. In eternity or perpetuity time would have no value.

But time is unlike money in that we must spend it. We cannot choose to hoard our time in the same way we can hoard money in our savings accounts. Each day we must pay our debt of personal hours and minutes to history. When we come to great time thresholds, like the end of the year, we have no choice but to step over. Although in theoretical physics time is not necessarily unidirectional, in our everyday Newtonian lives, it is. This inexorable arrow of time, an arrow that neither stops nor hesitates, is the cause of some of our most profound emotions.

For psychological time is not the same as clock time. Clock time is cold and runs with a metronomic regularity. Psychological time often drips with emotion and can speed up or slow down depending on our state of mind.

Emotions evoked by the past are nostalgia and regret. The emotions evoked by the future are anticipation and dread. On one hand, the expectation of something good evokes feelings of anticipation and, perversely, makes our own personal experience of time slower. Just ask any child waiting for Santa to arrive. On the other, the expectation of something bad evokes feelings of dread. Like Faustus awaiting death, we tend to face catastrophe with a wish that time would stop or slow down. How many of us, like Faustus, have been tempted to shout:

Stand still, you ever moving spheres of heaven,
That time may cease, and midnight never come.
Fair nature’s eye, rise, rise again, and make
Perpetual day; or let this hour be but
A year, a month, a week, a natural day!

Yet Faustus for all his diabolical powers cannot stop time: "The stars still move, time runs, the clock will strike!" How well Marlowe captures the fact that it is Faustus’ very dread that makes his personal time run more quickly.

Human emotions, experienced in moderation, are certainly good, but when these time-related emotions—anticipation, dread, nostalgia, and regret—completely consume us, we become ill. They wash away any positive, appealing qualities in our personal time. As the Buddhists will tell you, the only solution is to try to live fully in the present.

Yes, time must be spent; the trick is to spend it wisely. The Roman writer Seneca counseled his friend Lucilius that "certain moments are torn from us, some are gently removed, and others simply glide beyond our reach." The most disgraceful way to lose time, however, is to let it slip away carelessly. "Hold every hour in your grasp " Nothing, Lucilius, is ours, except time."

With the coming of the mechanical clock in the 14th century, the hour rather than the day became the standard unit of work time, and the insistence on using time profitably became a moral obligation. In the 15th century, Thomas a Kempis in the Imitation of Christ wrote "It is sad that you do not employ your time better " The time will come when you will long for one day or one hour in which to amend; and who knows whether it will be granted?" This lesson was dramatically portrayed in the ending of Dr. Faustus . Historian David Landes notes that "In an age of clocks, time thrift meant clock watching." If time is precious for saving one’s soul, it is also precious for making money. The 15th century Italian Leon Battista Alberti wrote in his diary:

In the morning when I get up, the first thing I do is think " what am I going to do today" So many things: I count them, think about them, and to each I assign its time. I’d rather lose sleep than time, in the sense of the proper time for doing what has to be done. The important thing is to watch the time, and assign things by time, to devote oneself to business and never lose an hour of time. He who knows how not to waste time can do just about anything.

Mr. Alberti knew in the 15th century what Ben Franklin declared in the 18th: time is money. The important thing is to regulate one’s life by the clock, to assign appropriate tasks to each hour. Not to waste a single minute.

There is certainly a kind of wisdom in time thrift and clock watching. One’s personal time on earth is a limited commodity. Just as we should be good stewards of our property, we should strive to be good stewards of our time. At the same time, however, we can become slaves to the clock. The ticks of the metronome can become lashes of a whip. The web of time can become a prison house. If we are driven each minute of the day by schedules and deadlines, especially other people’s deadlines, time becomes oppressive. There is a big difference between Mr. Alberti, sitting in his bed seemingly planning his day with complete freedom, and the lives of most of us, who owe large parts of our days to others. And even if our overflowing agendas contain nothing but our own activities, we can still become slaves of time. Perversely, the busier we are, the faster runs our sense of time. To slow time down, it seems, you need to exchange business for leisure.

That brings us, finally, to the lovely song by James Taylor: "The secret of life is enjoying the passage of time." We might agree with the conclusion but be confused by the means. How can one enjoy time when each passing second makes us poorer" Taylor advocates a powerful change in attitude. We must shift from being time misers to being time connoisseurs. Since we must spend our allotment of time whether we want to or not, let us savor it as a gift. Let us slow down our psychological clocks by being somewhat careless of time, "slidin’ down and glidin’ down" through the hours, minutes, and seconds. Rather than filling each minute obsessively with activity, let us "try not to try too hard."

Leon Battista Alberti and James Taylor mark out two extreme positions with respect to the gift of time. I suspect that each of us will find our own most comfortable position somewhere in the continuum between those two positions. The more ambitious among us will favor Alberti’s solution; those of us who are more free-spirited with favor Taylor’s. Wherever we fall, however, the yin of time discipline must be balanced by the yang of time savoring. For time is not only like money, it is also like food, something to be consumed. Who among us would want to rush through the many sweet and salty courses of life’s meal"

The holidays are certainly one of those periods when we should savor life. The borderlands of time are alive with significance, which can only be appreciated by slowing down. There will be time enough for schedules and deadlines in the new year. Whether we want them or not, they will come "just in time." The holidays belong to the James Taylors among us. Gazing at the lights, the food, the friends and family, who is not tempted to sing: "Isn’t that a lovely ride, oh, Momma yes. See me slidin’ down and glidin’down. Try not to try too hard. It’s just a lovely ride."