Keeping Time

Tracking the Cycles of Sun, Moon, & Earth

“The only reason for time is so everything doesn’t happen at once.”

—Albert Einstein


Before clocks and calendars, the turning of Earth and cycles of the Sun, Moon, and stars were how humans tracked time. A day is one rotation of Earth, and one cycle of the phases of the Moon gave us the month, while Earth’s circuit around the Sun is the year. Tracking days, months, and larger divisions of time has ancient roots, as the human need to move with cycles of time is universal. Time relates to everything from cooking and gardening to music and medicine.

Archaeologists have reconstructed methods of keeping time that reach back to prehistoric periods. Researchers have deduced from excavated tally sticks that people counted days in relation to the Moon’s phases as early as the Upper Paleolithic (Stone) Age, 50,000 years ago. Ancient cultures such as the Inca, Maya, and Hopi, and other American Indian tribes, as well as Babylonians, Buddhists, and Hindus perceive time like a wheel. Time is experienced as cyclical, not linear, consisting of repeating cycles that happen in measured ages and states of development from the birth of the Universe until its end. According to the large cycle of precession, Hindu cosmology has a wheel of ages called yugas that range from light to dark. The Greek and Roman system perceived ages that ranged from an idyllic Golden Age to the current Iron Age that is filled with conflict and pain.

In the ancient Greek view, time was seen in two ways—Chronos and Kairos. The first referred to numeric or chronological time since Chronus was the personification of time. Kairos conveyed the idea of “the right moment” and is related to “divine timing.” Kairos is qualitative while Chronos is quantitative, and casting and interpreting an astrology chart requires both. According to the Hebrew Qabalah, time is a paradox and an illusion, as both past and future are perceived as simultaneously “present.” In the Old Testament book of Ecclesiastes, traditionally attributed to Solomon, time has often been translated from Hebrew as “age,” and seen as the unfolding of prophecies or predestined events. The Islamic and Judeo-Christian worldview tends to regard time as linear and directional, beginning with a divine act of creation. Time will end at some point teleologically, an ending understood to be intrinsic to the order of things.

Ancient calendars were usually lunisolar and were based on observation, requiring an intercalary month to bring the solar and lunar years into alignment. The Moon’s motion is complex because the Sun, Earth, and planets all exert gravity. The Moon rotates on its axis every 27.5 days, the same time it takes to circle Earth. This is called the sidereal period as the Moon returns to the same place relative to the stars. This dual motion is why the same side of the Moon is always visible to Earth. However, the far side is not always dark, since the Moon’s rotation exposes the whole surface to sunlight. Even though we don’t ever see the “dark side” from Earth, it is fully illuminated at the New Moon.

The synodic month is the most familiar and is defined as the interval between two consecutive lunar phases, as seen by an observer on Earth. The mean synodic length (rounded) is 29.5 days. The distinction between sidereal and synodic cycles was recognized in historical times in Babylonian lunar astronomy. The synodic period is longer because while the Moon is orbiting Earth, we travel about thirty degrees of arc each month in our annual trek around the Sun. The Moon has to compensate since the Earth-Moon system is orbiting the Sun in the same direction as the Moon is orbiting the Earth, so it takes about 2.2 days longer for the Moon to return to the same apparent position with respect to the Sun. Dividing the number of days of the year by the 29.5 days of the synodic lunar cycle yields about 12.37 New Moons or Full Moons each year, which are called lunations. Numerous cultures have wrestled with the problem of solar-lunar cycles, and many cultures used multiple calendars to distinguish sacred, secular, and agricultural domains.

Regardless of how time is understood philosophically, clocks mark the passage of time and calendars organize segments of time. Water clocks are some of the oldest time-measuring instruments. Where and when they were first invented is unknown given their great antiquity. The simple bowl-shaped outflow water clock existed in Babylon and Egypt around the sixteenth century BCE. India and China also have early evidence of water clocks. Some authors claim that water clocks appeared in China as early as 4000 BCE. The hourglass, or sand clock, is an ancestor of the modern kitchen timer and is thought to have developed from the water clock in ancient India. The sand flows down from the upper bowl, which is seen as the past, through the narrow neck that represents the present moment, and into the lower bowl that is seen as the future.

A sundial tells the time of day by the shadow cast by the apparent movement of the Sun. As the Sun moves across the sky, the shadow aligns with different hour lines that are marked on the dial to indicate the time of day. The earliest sundials known from archaeological finds are shadow clocks used in Babylonian astronomy 3,500 years ago. An ancient sundial from Egypt, in the Valley of the Kings, dates to 2,500 years ago.

Calendars are explicit schemes for keeping time and organizing dates for social, religious, commercial, or administrative purposes. Calendars give names to periods of time, such as days, weeks, months, and years. The word calendar comes from calends, the term for the first day of the month in the Roman calendar. It’s related to the verb calare, “to call out,” referring to the announcement that the first sliver of new moon had been seen, beginning the month. Latin calendarium meant “account book,” or “register,” as accounts were settled and debts were collected on the calends of each month.

Historically, the first formalized calendars date to the Bronze Age around 5,000 years ago and were dependent on the development of writing in the ancient Near East. The Sumerian calendar is the earliest known, followed by Egyptian, Assyrian, and Elamite calendars. A larger number of calendar systems of the ancient Near East appear in the Iron Age archaeological record, based on the Assyrian and Babylonian calendars. A 1079 calendar reform in Persia, led by Khayyam, measured the length of the year as 365.24219858156 days. Since the length of the year changes in the sixth decimal place over a lifetime, this was remarkably accurate. The length of the year at the end of the nineteenth century was 365.242196 days, while today it is 365.242190 days.

The Roman calendar contained ancient remnants of a pre-Etruscan ten-month solar year but was reformed by Julius Caesar in 45 BCE. The Julian calendar no longer depended on observation of the New Moon but followed an algorithm of introducing a leap day every four years. However, this created a still ongoing dissociation of the calendar month from the lunation. The Gregorian calendar was introduced as a refinement to the Julian calendar in 1582 CE and is still the main calendar in worldwide use today.

The Gregorian calendar has twelve fixed months of differing lengths; so as the cycles change, the shorter lunar cycle (29.5 days) can fall twice in a calendar month. This creates an artifact in our modern calendar that is called a “blue moon.” This is not because the Moon appears blue, but because two Full Moons fall in one calendar month. There is also a “dark moon,” two New Moons in a calendar month. A blue moon month typically occurs once in 2.7 years. However, 2018 will have two blue moon months, one in January and one in March, causing February of 2018 to be a month without a Full Moon. The last time this occurred was in 1999 when the blue moons also occurred in January and March. This cyclical recurrence is because of the nineteen-year Metonic cycle of lunar phases.

The discovery of this cycle is credited to Meton (432 BCE) an Athenian astronomer. Mathematically, nineteen tropical years have 6,939.60 days, while 235 synodic months have 6,939.69 days. After nineteen years, the phases of the Moon occur on the same dates of the year, after which the Moon’s phases recur on the same days of the solar year, or year of the seasons. There are 235 lunar months and 236 Full Moons during one Metonic cycle. There are also 228 calendar months, so at least eight of those months will have two Full Moons.

Since this is almost equal to twenty eclipse years (6,932.4), it is also possible for a series of four or five eclipses to occur on the same dates nineteen years apart. Edmund Halley, of comet fame, mistakenly linked the naming of the cycle of 223 synodic months with Suidas, a tenth century Greek, who had actually called the Metonic cycle Saros. Halley wrongly named the eclipse cycle Saros, and the name stuck.

Astrologically, the Moon moves thirteen degrees a day through an astrological sign and makes thirteen orbits of Earth in a year. Usually, there is one New Moon and one Full Moon in each of the twelve zodiac signs. Symbolically, the cycles and phases of the Moon’s light offer periodic illumination into our individual and collective natures. Just as space travel has given us a glimpse of the Moon’s hidden side, the relationship between Earth and Moon is a journey of ever-changing, but ever-increasing, light and consciousness.

The Moon represents our instincts, memories, habitual behaviors, and the general inheritance of the past. The Moon is seen symbolically as our lost psyche, partly hidden in shadow and separated from our waking consciousness as we journey through time. The Moon reflects our evolving personalities. The hidden side conceals our habitual selves and holds unconscious patterns that need to be healed or reclaimed. The dark side is the realm of depth psychology analysis and astrological insight that can reveal what’s in the shadow and work to bring these issues into the light of conscious awareness. Astronomy is science, based on observation and measurement. Astrology is an interpretative discipline that applies meaning and correspondences to what has been observed over thousands of years. Not so long ago they were the same. I believe we’ve lost a great deal as a result of the radical severance of these disciplines. When we separate meaning from measurement, we cleave the mind and heart.

Increasingly, our personal electronic devices display both calendars and clocks simultaneously, further separating us from the cycles and rhythms that inform both. Clocks and calendars are useful devices, but they make it easy to lose touch with the real rhythms we’re biologically and spiritually attuned to. Artificial light disconnects us from the night, sweeping lunatics and werewolves under the carpet, and denying our instinctual response to deep impulses that dwell in the darkness. Technology is a fact of modern life and has given rise to many timesaving inventions. However, lest we lose touch with nature, we should pay attention to the recurring cycles that keep our hearts, our personal ticking clocks, in rhythm and harmony with the natural world.

By Julie Loar