The Astronomical Calendar: Sky Events Through the Year

The Observatory Almanac — Calendars & Time

The sky is the oldest calendar humanity has ever used. Long before writing, before agriculture, before cities, our ancestors watched the sun, moon, stars, and wandering planets to understand where they were in the year — and in the cosmos. What follows is a guide to the sky's recurring events: the dependable cycles that have governed human time-keeping for millennia, alongside the spectacular transient phenomena that remind us we live in a dynamic, ever-changing universe.

Solar Events: The Pillars of the Year

The Solstices

The word "solstice" derives from the Latin sol (sun) and sistere (to stand still) — describing the apparent pause in the sun's northward or southward movement before it reverses direction.

Summer Solstice — approximately June 20–21 (Northern Hemisphere)
The longest day of the year. The sun reaches its maximum northern declination, rising and setting at its most northerly points on the horizon, and climbs to its highest noon altitude. At latitudes above 66.5°N (the Arctic Circle), the sun never fully sets on this date — the midnight sun. Every culture in the Northern Hemisphere has noted this turning point, from Stonehenge (precisely aligned to the midsummer sunrise) to Midsommar in Scandinavia to the Inca celebration of Inti Raymi.

For the Southern Hemisphere, June 21 is the Winter Solstice — the shortest day. Southern midsummer falls around December 21.

Winter Solstice — approximately December 21–22 (Northern Hemisphere)
The shortest day and longest night. The sun reaches its minimum northern declination. This is the astronomical turning point of winter — though the coldest weather is still weeks away (due to the thermal lag of land and ocean). Virtually every ancient culture regarded the winter solstice as a moment of cosmic rebirth: Yule in Germanic tradition, Dongzhi in China, the Roman Saturnalia, the Zoroastrian Yalda Night (marking the triumph of Ahura Mazda over darkness). The deliberate placement of Christmas near the winter solstice reflects this universal impulse toward light and renewal in the darkest time.

The precise moment of solstice can be calculated to the second. In 2025, the Northern Hemisphere summer solstice occurs on June 20 at 22:42 UTC.

The Equinoxes

"Equinox" means "equal night" — though in practice, the date when day and night are exactly equal is slightly different from the astronomical equinox due to atmospheric refraction and the definition of sunrise/sunset (the moment the sun's upper limb crosses the horizon).

Vernal (Spring) Equinox — approximately March 20–21 (Northern Hemisphere)
The sun crosses the celestial equator moving northward. Day and night approach equality; the sun rises due east and sets due west. The vernal equinox is used to calculate Easter (see Religious Calendars section), Persian Nowruz, and the Bahá'í New Year. Many ancient monuments — including Chichen Itza's El Castillo pyramid — are aligned to dramatically mark the equinox with light and shadow.

Autumnal Equinox — approximately September 22–23 (Northern Hemisphere)
The sun crosses the celestial equator moving southward. Harvest festivals worldwide cluster around this time, as it marks the full maturity of summer's growth. The Harvest Moon (see below) occurs nearest this equinox.

The Lunar Cycle

Phases of the Moon

The moon completes one orbit around Earth every 27.3 days (the sidereal month, measured relative to the stars). But the lunar phase cycle — new moon to new moon — takes approximately 29.5 days (the synodic month), because Earth has moved in its orbit around the sun during those 27.3 days, requiring the moon to travel a bit farther to "catch up" to the same position relative to the sun.

The eight primary phases:

New Moon: The moon is between Earth and the sun; the illuminated face points away from us. The moon rises and sets with the sun — invisible to the naked eye. This is the darkest night.
Waxing Crescent: A thin sliver of light appears on the right (western) edge, visible just after sunset in the west. The rest of the moon is sometimes visible as "Earthshine" — sunlight reflected from Earth onto the unlit lunar surface.
First Quarter: The moon has completed a quarter of its cycle. The right half is illuminated; the moon is high in the south at sunset, setting around midnight.
Waxing Gibbous: More than half illuminated, growing toward full. Rises in the afternoon, well up by sunset.
Full Moon: The moon is opposite the sun; its entire face is illuminated. Rises at sunset, sets at sunrise — in the sky all night long. The full moon is 14× brighter than first quarter.
Waning Gibbous: Illumination decreasing from the right side. Rises after sunset, visible in the morning sky.
Last Quarter: Left half illuminated; rises around midnight, high in the south at dawn.
Waning Crescent: A thin sliver on the left (eastern) edge, visible in the pre-dawn eastern sky. Rises in the small hours before sunrise.

Full Moon Names

The traditional names for each month's full moon come primarily from Algonquian peoples of North America, adapted and popularized by colonial almanacs and later modern astronomy culture. Other cultures have their own naming traditions, but these are the most widely used in contemporary Western contexts:

Month	Name	Origins and Meaning
January	Wolf Moon	Named for the howling of hungry wolf packs outside winter villages. Also: Old Moon, Cold Moon
February	Snow Moon	Typically the month of heaviest snowfall. Also: Hunger Moon, Bone Moon
March	Worm Moon	Earthworms begin to appear as frozen ground thaws. Also: Crow Moon, Crust Moon, Sap Moon
April	Pink Moon	Named not for its color but for the herb moss pink (Phlox subulata) blooming in spring. Also: Egg Moon, Fish Moon
May	Flower Moon	Flowers bloom abundantly. Also: Corn Planting Moon, Milk Moon
June	Strawberry Moon	The brief strawberry harvesting season. Also: Mead Moon, Rose Moon
July	Buck Moon	Male deer begin growing new antlers. Also: Thunder Moon, Hay Moon
August	Sturgeon Moon	Great Lakes tribes' prime time for catching sturgeon. Also: Red Moon, Green Corn Moon
September	Harvest Moon	The full moon nearest the autumnal equinox — rises near sunset for several nights, historically extending farmers' working hours
October	Hunter's Moon	Traditionally a time to hunt fattened deer by the light of this bright moon. Also: Travel Moon, Dying Grass Moon
November	Beaver Moon	Time to set beaver traps before waters froze. Also: Frost Moon, Freezing Moon
December	Cold Moon	Long nights and cold temperatures. Also: Long Night Moon, Oak Moon

The Harvest Moon: Special Properties

The Harvest Moon (and to a lesser extent the Hunter's Moon) has a unique property: near the autumn equinox, the angle of the moon's orbit relative to the horizon is shallow, causing it to rise only 20–30 minutes later each night rather than the usual 50 minutes. This means several consecutive nights of nearly-full moon rising near sunset — a natural extension of daylight that farmers historically depended upon for harvest.

Blue Moons

A "blue moon" in popular usage refers to the second full moon in a single calendar month (since months average 30–31 days but the lunar cycle is 29.5, this happens roughly every 2–3 years). This yields the phrase "once in a blue moon." The moon doesn't actually turn blue — though volcanic eruptions or large wildfires can put enough particulates in the atmosphere to give the moon a blueish tint.

A less common but historically earlier definition: the third full moon in a season that contains four full moons (usually seasons have three).

Supermoons

The moon's orbit is an ellipse, not a perfect circle. At its closest approach to Earth (perigee), the moon can be approximately 14% closer than at its farthest point (apogee). When a full moon occurs near perigee, it appears up to 14% larger and 30% brighter than a full moon at apogee. This is colloquially called a "supermoon." The term has no precise astronomical definition and varies by formula, but typically 3–4 supermoons occur each year.

Meteor Showers

Meteor showers occur when Earth's orbit passes through streams of debris left by comets (and occasionally asteroids). As these particles — typically sand-grain to marble size — enter Earth's atmosphere at high speed, friction superheats the air around them, creating brief luminous streaks of ionized gas. The shower appears to radiate from a single point in the sky (the radiant), named after the constellation in which it lies.

The Major Annual Showers

Quadrantids — Peak: January 3–4
Parent body: Asteroid 2003 EH1 (possibly a dormant comet fragment)
Rate: Up to 120 meteors/hour at peak (ZHR)
Notes: One of the strongest showers but with a very brief peak (6–12 hours), making it weather-sensitive and often missed. The radiant is in the now-defunct constellation Quadrans Muralis (now part of Boötes). Best viewed from northern latitudes.

Lyrids — Peak: April 21–22
Parent body: Comet Thatcher (C/1861 G1)
Rate: 10–20 meteors/hour; occasional outbursts to 100+
Notes: One of the oldest recorded meteor showers — Chinese records from 687 BCE describe "stars falling like rain." Occasionally produces brilliant fireballs.

Eta Aquariids — Peak: May 5–6
Parent body: Halley's Comet
Rate: 20–40 meteors/hour (North); 40–85 (South)
Notes: Debris shed by Halley's Comet. Best from the Southern Hemisphere, where the radiant (near Aquarius) is higher. Notable for its "persistent trains" — glowing trails lasting seconds after the meteor itself.

Delta Aquariids — Peak: July 28–29
Parent body: Possibly Comet 96P/Machholz
Rate: 15–20 meteors/hour
Notes: A diffuse, long-lasting shower with multiple sub-peaks. Best from southern latitudes. Often observed simultaneously with early Perseids.

Perseids — Peak: August 11–13
Parent body: Comet Swift-Tuttle (orbital period ~130 years)
Rate: 50–100+ meteors/hour
Notes: The most popular meteor shower in the Northern Hemisphere — warm nights, no need to wait for the radiant to rise, excellent rates. Swift-Tuttle deposits rich debris trails, and in some years the Perseids "outburst" to 200+ per hour. The radiant is in Perseus, but meteors streak across the whole sky. The peak coincides with summer vacation in many countries.

Orionids — Peak: October 20–21
Parent body: Halley's Comet (second shower from Halley's debris)
Rate: 10–20 meteors/hour
Notes: Swift, bright meteors with persistent trains. The radiant is near Betelgeuse in Orion, which rises around midnight — the shower improves through the early morning hours.

Taurids — Peak: Southern Taurids November 4–5; Northern Taurids November 11–12
Parent body: Comet Encke
Rate: 5–10 meteors/hour (each branch)
Notes: Low rates but famous for producing "Halloween fireballs" — spectacularly bright bolides associated with larger debris in the Taurid stream. The shower has an exceptionally long active period (September–December).

Leonids — Peak: November 16–17
Parent body: Comet Tempel-Tuttle (orbital period ~33 years)
Rate: 10–15 meteors/hour typical; periodic storms of thousands per hour
Notes: In years when Tempel-Tuttle passes close to its perihelion, the Leonids produce legendary meteor storms. The 1833 Leonid storm (estimated 100,000 meteors per hour) is credited with launching the scientific study of meteor showers. The most recent significant outburst was in 2001–2002. The next major storm is uncertain but possible in the 2030s.

Geminids — Peak: December 13–14
Parent body: Asteroid 3200 Phaethon (a "rock comet")
Rate: 100–150 meteors/hour
Notes: Arguably the best overall meteor shower. The rates rival and often exceed the Perseids; the meteors are slower and many are vivid colored fireballs. Unusually, the parent body is an asteroid (or "extinct comet") rather than an active comet. The radiant is in Gemini, accessible from early evening. The main drawback: December cold.

Ursids — Peak: December 22–23
Parent body: Comet Tuttle (8P/Tuttle)
Rate: 5–10 meteors/hour; occasional outbursts
Notes: Often overlooked, falling near the winter solstice. The radiant is near Polaris — excellent for Northern Hemisphere observers since the radiant is circumpolar (never sets).

Observing Tips for All Showers

Dark sky is everything. Even modest light pollution can reduce observed rates by 50–80%. The Bortle scale (1 = perfect dark sky, 9 = city center) is a useful reference.
Let your eyes dark-adapt. Takes 20–30 minutes away from bright lights. Even a brief phone glance resets this.
Face away from the radiant. Meteors near the radiant are shorter (traveling more directly toward you) than those near the edges of your field of view.
Lie on your back. A sleeping bag on a ground pad and a clear view of the whole sky is more effective than any telescope.
Don't wait for the peak hour listed. Showers are active for days around peak. Peak ZHR (Zenithal Hourly Rate) assumes the radiant is directly overhead and a perfectly dark sky — actual observed rates are typically 50–60% of ZHR.

Eclipses

How Eclipses Work

Eclipses occur when the sun, Earth, and moon align precisely. The moon's orbit is inclined about 5° to Earth's orbital plane (the ecliptic), which is why eclipses don't happen every new and full moon — most months the moon passes slightly above or below the alignment.

The key geometrical features: the moon's shadow has two parts — the umbra (the dark inner cone where the sun is completely blocked) and the penumbra (the lighter outer cone where the sun is only partially blocked). Earth's shadow behaves similarly.

Types of Solar Eclipse

A solar eclipse occurs at new moon, when the moon's shadow falls on Earth.

Total Solar Eclipse: The moon's umbra touches Earth's surface — a small path (the "path of totality," typically 50–150 km wide) experiences totality. The sun's corona blazes into view; the sky darkens; stars appear; the temperature drops. Totality lasts from seconds to a maximum of about 7 minutes 31 seconds. Outside the path, a partial eclipse is seen. These are arguably nature's most spectacular events and inspire devoted "eclipse chasers" who travel the world to stand in the path.

Partial Solar Eclipse: The moon's penumbra covers a wide region. Only part of the sun's disk is covered by the moon.

Annular Solar Eclipse: When the moon is near apogee (farthest from Earth), its apparent size is too small to fully cover the sun. A ring (annulus) of sunlight surrounds the moon — the dramatic "ring of fire." Annular totality can last up to 12 minutes.

Hybrid (Annular-Total) Eclipse: Along parts of the path it is annular; along other parts, total — due to Earth's curvature. Rare and particularly scientifically interesting.

⚠️ Safety: Never look directly at a partial or annular eclipse without certified eclipse glasses (ISO 12312-2). Only during totality in a total solar eclipse is it safe to view with naked eyes — and only for the duration of totality.

Types of Lunar Eclipse

A lunar eclipse occurs at full moon, when Earth's shadow falls on the moon.

Total Lunar Eclipse (Blood Moon): The full moon passes entirely through Earth's umbra. The moon turns a deep reddish-brown — "blood red" — because Earth's atmosphere refracts and bends sunlight around Earth, casting a reddish light on the moon (the same effect that turns sunrises and sunsets red). Totality can last up to 1 hour 47 minutes. Safe to view with naked eyes.

Partial Lunar Eclipse: Only part of the moon enters Earth's umbra.

Penumbral Lunar Eclipse: The moon passes through Earth's penumbra only. The moon dims slightly but often no clear shadow boundary is visible. Subtle and often unnoticed.

Upcoming Notable Eclipses (2025–2030)

March 14, 2026 — Total Lunar Eclipse, visible from the Americas, Europe, Africa
August 12, 2026 — Total Solar Eclipse, path across Greenland, Iceland, Spain, Morocco — first total eclipse over continental Europe in nearly a decade
February 6, 2027 — Annular Solar Eclipse, Pacific and South America
August 2, 2027 — Total Solar Eclipse, Morocco, Libya, Egypt, Saudi Arabia, Yemen, Oman, India — maximum totality of 6 min 23 sec
July 22, 2028 — Total Solar Eclipse, Australia and New Zealand
2030s — Multiple total solar eclipses cross North America, Africa, and Asia

Planet Visibility

The Inner Planets

Mercury is the most elusive of the classical planets — never far from the sun in the sky (maximum elongation ~28°). It appears in the evening sky for several weeks, then crosses behind the sun (superior conjunction), then reappears in the morning sky, then crosses between Earth and the sun (inferior conjunction). Mercury is at its easiest in spring evenings (when the ecliptic is steeply angled) and autumn mornings. It never gets truly dark while Mercury is well above the horizon.

Venus dominates as the "Evening Star" or "Morning Star" — the brightest object in the sky besides the sun and moon, reaching magnitude −4.7 at maximum brilliance. Venus follows a similar pattern to Mercury but with much greater elongations (up to 47°). At maximum elongation, Venus can cast visible shadows in truly dark conditions. It shows phases through a small telescope, cycling from a large crescent to a smaller gibbous over its synodic period of 584 days.

The Outer Planets

Mars has a 26-month synodic cycle. Every 26 months it reaches opposition — directly opposite the sun, rising at sunset, highest at midnight, and at its brightest. But Mars's orbit is more elliptical than Earth's, so oppositions vary dramatically. A "great opposition" (when Mars is near its perihelion during opposition) brings it to magnitude −2.9 — outshining everything except Venus. A poor opposition has it only around magnitude −1. Between oppositions, Mars fades to magnitude +1.5 or dimmer and shrinks considerably through a telescope.

Jupiter is the brightest "star-like" object visible most of the year, reaching magnitude −2.9 at opposition. Its 12-year orbital period means it spends roughly a year in each zodiac constellation. Jupiter's four Galilean moons — Io, Europa, Ganymede, Callisto — are visible through binoculars as tiny dots that shift position night to night.

Saturn reaches approximately magnitude −0.4 at opposition — easily visible to the naked eye but not dramatically so. Its rings are its great spectacle through even a small telescope, but the naked eye sees only a steady golden "star." Saturn's rings were edge-on to Earth in early 2025, reducing their visibility.

Uranus (magnitude +5.7 at opposition) is technically visible to the naked eye under excellent dark skies and known position, but most observers need binoculars to identify it as a non-stellar disk.

Neptune (magnitude +7.8) requires binoculars or a small telescope.

Conjunctions and Notable Events

Planetary conjunctions — when two planets appear close together in the sky — are visually striking even though the planets are actually vastly separated in three-dimensional space. The "Christmas Star" of 2020 was a spectacular Jupiter-Saturn conjunction, their closest approach in 400 years.

Other notable configurations: - Planetary parade: When several planets are visible simultaneously in the sky — rare to have 4–5 planets strung along the ecliptic. - Planet-Moon conjunction: The waxing crescent moon passes each bright planet monthly, creating brief but beautiful pairings. - Elongation events: Mercury and Venus at greatest elongation offer the best opportunities to observe them in a dark sky (shortly after sunset or before sunrise).

Comets

Comets are frozen remnants of the early solar system — "dirty snowballs" of ice, rock, and dust. When they approach the inner solar system, solar radiation and the solar wind heat and erode their surface, releasing gas and dust that form the characteristic coma (a fuzzy atmosphere) and tails: a bright dust tail curving away from the comet's direction of motion, and a fainter, straighter ion tail pointing directly away from the sun.

Most comets are too faint to see without a telescope. Spectacular "naked eye comets" occur once every few years to once per decade, and truly spectacular comets (bright enough to be seen in daylight or with long tails covering much of the sky) perhaps once or twice per century.

Notable Periodic Comets

Halley's Comet (1P/Halley) — Orbital period: ~75–76 years
Last perihelion: 1986. Next perihelion: mid-2061. Halley's Comet gave rise to two annual meteor showers (Eta Aquariids and Orionids). Its 1910 apparition — when Earth passed through its tail — sparked mass hysteria. The 1986 apparition was disappointing for most observers; the 2061 apparition should be spectacular.

Comet Encke (2P/Encke) — Orbital period: 3.3 years
The shortest known orbital period of any comet. Parent of the Taurid meteor showers. Never a spectacular comet, but accessible by telescope every few years. Extensively studied.

Comet Swift-Tuttle (109P) — Orbital period: ~130 years
Parent of the Perseids. Last perihelion: 1992. Next perihelion: 2126.

Comet Wirtanen (46P) — Orbital period: 5.4 years
Had a memorable close approach to Earth in December 2018, becoming a binocular object with a large, diffuse coma.

Comet Tsuchinshan-ATLAS (C/2023 A3) — 2024 apparition
A magnificent recent example: this comet achieved naked-eye visibility in October 2024, displaying a brilliant ion tail that stretched tens of degrees across the sky for many observers.

International Space Station

The International Space Station (ISS) orbits Earth at approximately 400 km altitude, completing an orbit every 90 minutes. It is the third-brightest object in the night sky (after the moon and Venus) — easily visible to the naked eye as a steady, fast-moving white point of light, crossing the sky in about 5–6 minutes.

Visibility is local and precise — an ISS pass visible from London may not be visible from Paris an hour later. The ISS is visible only around dawn and dusk, when the station is in sunlight but the observer is in darkness.

How to track: - NASA Spot the Station: spotthestation.nasa.gov — sign up for email/text alerts - Heavens-Above: heavens-above.com — detailed pass predictions with sky charts - ISS Detector app: Mobile apps provide push notifications for upcoming passes - Stellarium app: Includes satellite tracking with ISS orbit data

Other satellites (Hubble Space Telescope, Chinese Space Station Tiangong, and various bright Starlink "trains") are also trackable via these resources.

Deep Sky Objects Visible to the Naked Eye

Beyond the solar system, several remarkable deep-sky objects are visible without any optical aid under dark skies:

The Milky Way — Our galaxy's disk seen from within. Under dark skies (Bortle 3 or better), it appears as a luminous band arching across the sky from horizon to horizon — brighter and more complex toward the center of the galaxy in Sagittarius. The core is richest from about June through September for mid-northern latitudes.

Andromeda Galaxy (M31) — Visible to the naked eye as a fuzzy oval patch in the constellation Andromeda, about 2.5 million light-years away — the farthest thing normally visible to the unaided eye. Under suburban skies it requires knowing exactly where to look; under dark skies it is obvious and stunning. At full size (extending 6× the apparent diameter of the moon), it appears to require dark-sky conditions to reveal.

Large and Small Magellanic Clouds — Two irregular dwarf galaxies, satellites of the Milky Way, visible from the Southern Hemisphere as large misty patches — the LMC at 160,000 light-years and the SMC at 200,000 light-years. Every southern-hemisphere stargazer knows them; they were used for navigation and feature prominently in Indigenous Australian astronomy.

Pleiades (Seven Sisters, M45) — The most famous star cluster in the sky. Most observers see 6 stars (one "lost" Pleiad of mythology); under dark skies, the cluster resolves into dozens of members embedded in blue reflection nebulosity. In Taurus, best visible in winter for Northern Hemisphere observers. Mentioned in the Bible (Job, Amos), Homeric poems, and Aboriginal Australian stories.

Orion Nebula (M42) — The middle "star" of Orion's sword is not a star at all but a stellar nursery 1,344 light-years away. Under dark skies, the naked eye reveals a soft glow; binoculars show the bright central region and the Trapezium star cluster at its heart. One of the most-photographed objects in the sky.

The Hyades — The nearest open star cluster (153 light-years), forming the V-shape of Taurus the Bull's face. Obvious to the naked eye, a lovely binocular object.

Omega Centauri (ω Cen) — The largest and most massive globular cluster in the Milky Way — 150,000 stars packed into a sphere 100 light-years across, 17,000 light-years away. Visible to the naked eye as a "fuzzy star" from southern latitudes; it was catalogued as a star by Ptolemy before its true nature was understood.

Perseus Double Cluster (NGC 869/884) — Two open star clusters side by side, visible to the naked eye under dark skies and spectacular through binoculars or a small telescope.

Dark Sky Preservation and the Bortle Scale

The Bortle Scale

Developed by John Bortle and published in Sky & Telescope in 2001, the Bortle Dark-Sky Scale rates sky darkness on a scale from 1 to 9:

Class	Description	Typical Setting
1	Exceptional dark sky	Remote desert, high mountain
2	Truly dark sky	Remote wilderness
3	Rural sky	Remote farmland
4	Rural/suburban transition	Near small town
5	Suburban sky	Suburbs
6	Bright suburban sky	Dense suburbs
7	Suburban/urban transition	Near city
8	City sky	City
9	Inner city sky	Downtown

Today, over one-third of humanity — including 80% of North Americans and 60% of Europeans — cannot see the Milky Way from where they live. The consequences extend beyond aesthetics: artificial light disrupts circadian rhythms in humans and wildlife, disorients migrating birds, and is linked to insect population declines.

International Dark Sky Places

The International Dark-Sky Association (IDA) certifies: - Dark Sky Sanctuaries — the most pristine, remote sites - Dark Sky Parks and Reserves — protected areas with excellent darkness - Dark Sky Communities — towns that have adopted dark-sky ordinances

Notable examples: Aoraki Mackenzie International Dark Sky Reserve (New Zealand), NamibRand Nature Reserve (Namibia), Galloway Forest Dark Sky Park (Scotland), Cherry Springs State Park (Pennsylvania, USA).

Practical Dark-Sky Tips

Travel 50+ km from major cities to reach Bortle 4–5 skies; 100+ km for Bortle 3.
New moon windows: The two weeks centered on new moon are darkest.
Blue light avoidance: Switch devices to red mode or use red flashlights (red light preserves dark adaptation).
Allow 20–30 minutes for your eyes to adapt. Pupil dilation alone isn't sufficient — photopigment regeneration takes time.
Weather and transparency: Clear skies are necessary but not sufficient. "Transparency" (atmospheric clarity) and "seeing" (atmospheric stability) are separate qualities.

The sky is patient. It has been watched by every human who has ever lived, and it will be watched by every human who ever will. The cycles described here were old before our earliest cities, and they will continue long after our last. To know the sky is to know something permanent in an impermanent world.

The Observatory Almanac | Calendars & Time | Section 12