Calendars. They hang on the wall or sit on the counter in my house or at my office. Probably in your homes and workplaces, too. Some are funny — Dilbert or The Far side — while others are picturesque or even beautiful. The one hanging over my desk displays cityscapes from Germany, a new one each month.

Other calendars are invisible, hiding in memories or in the tissues of a body or the components of a dishwasher.

The first set of calendars usually carry reminders about the present or reveal a path to future events or appointments. The second set, the invisible ones, do the same, but also often do something that is nearly the opposite: measure the time that’s passed against the time that’s left, keeping track of how my body has used up a certain many heartbeats or the dishwasher pump has drained the appliance this or that many days.

Another thing is interesting about calendars: They don’t all record the same kinds of years, months, weeks or even days. Calendars can be personal, ecclesiastical, financial or academic. Jan. 1 was the first day of 2010, but three weeks ago, April 15 was the final day of a significant calendar for most Americans and their accountants.

One of the more important calendars for me, and for most families with members in school, is the academic calendar. That year runs from the first day of classes in late summer or early fall until the last day of classes in late spring or early summer.

Mine officially ended the middle of last week, when I submitted final grades for the courses from the second half of the 2009-2010 academic year. The new year officially begins with orientation and the first week of classes at the end of August. Right now I’m working in “limbo” time. Technically, it’s still part of the last academic year, but most students have gone home to summer jobs, to their internships or to the post-graduation job search.

Another important calendar for our family is the church year, which begins with the first Sunday in Advent, at the end of November or the beginning of December. It’s a familiar cycle of stories and worship for all the members of the household, as the ancient pattern repeats the rituals commemorating birth, baptism, death and resurrection.

The invisible calendars are more personal than the ones hanging on the wall. Some, indeed, can be traced on paper calendars: The number of years since marriage ended bachelorhood or the death of parents and grandparents. Others, however, don’t lend themselves to tracing on any external calendar.

How many years, months, days and hours since the last phone call or hug from mom? How many since I tasted Grandma’s chicken soup, Grossmutter’s rotegritse or ate a fresh picked tomato from Grossvater’s garden? How many since that game of crazy eights with my cousins at the lake house, the game that wouldn’t end? Those calendars are recorded only within the synapses of my brain, traceable only via my imperfect memories.

Time has been written about by poets and philosophers for thousands of years. Scientists have spun theories as they try to explain the workings of time’s arrow. So much ink has been spilled — and now pixels displayed — in texts about time that many have become clichés (don’t worry, I won’t include a list here), but I’m not convinced that all those words have helped advance or clarify understanding.

We humans live — I live — in a whirling chaos of calendars, with years and eras beginning or ending every time I wake up or even turn around.

What’s it all mean? Which futures are the most important, the ones for which I can and should plan my actions? Which futures are the ones I can’t plan for, the ones in which I can only react to life’s random events? Can I alter by even one atom the past’s hold on both present and future? The chaos, the lack of certainty, drives me crazy.

Perhaps understanding is not possible. Perhaps uncertainty is inevitable. And maybe that’s for the best. Giving up on attempts to plan for every contingency or alter the past’s trajectory, ending attempts to control the flight of time’s arrow, brings a kind of freedom to fully embrace the present. After all, the only time in which we can live is today, the arena of action which reveals what sort of person we are … or are becoming.

Albert Lea resident David Rask Behling teaches at Waldorf College in Forest City, Iowa, and lives with his wife and children in Albert Lea. His column appears every other Tuesday.