January

Key takeaways

January belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect January to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of January from memory before moving on to harder problems.

Reference excerpt

January is the first month of the year in the Julian and Gregorian calendars. Its length is 31 days. The first day of the month is known as New Year's Day. It is, on average, the coldest month of the year within most of the Northern Hemisphere (where it is the second month of winter) and the warmest month of the year within most of the Southern Hemisphere (where it is the second month of summer). In the Southern hemisphere, January is the seasonal equivalent of July in the Northern hemisphere and vice versa. Ancient Roman observances during this month include Cervula and Juvenalia, celebrated January 1, as well as one of three Agonalia, celebrated January 9, and Carmentalia, celebrated January 11. These dates do not correspond to the modern Gregorian calendar.

History

January (in Latin, Ianuarius) is named after Janus, the god of beginnings and transitions in ancient Roman religion and mythology. Traditionally, the original Roman calendar consisted of 10 months totaling 304 days, winter being considered a month-less period. Around 713 BC, the semi-mythical successor of Romulus, King Numa Pompilius, is supposed to have added the months of January and February, so that the calendar covered a standard lunar year (354 days). Although March was originally the first month in the old Roman calendar, January became the first month of the calendar year either under Numa or under the Decemvirs about 450 BC (Roman writers differ). By contrast, each specific calendar year was identified by the names of the two consuls, who entered office on March 15th until 153 BC, at which point they started entering office on January 1st. Various Christian feast dates were used for the New Year in Europe during the Middle Ages, including March 25 (Feast of the Annunciation) and December 25. However, medieval calendars were still displayed in the Roman fashion with twelve columns from January to December. Beginning in the 16th century, European countries began officially making January 1 the start of the New Year once again—sometimes called Circumcision Style because this was the date of the Feast of the Circumcision, being the seventh day after December 25. Historical names for January include its original Roman designation, Ianuarius, the Saxon term Wulf-monath (meaning "wolf month") and Charlemagne's designation Wintarmanoth ("winter / cold month"). In Slovene, it is traditionally called prosinec; the name, associated with millet bread and the act of asking for something, was first written in 1466 in the Škofja Loka manuscript. According to Theodor Mommsen, 1 January became the first day of the year in 600 AUC of the Roman calendar (153 BC), due to disasters in the Lusitanian War. A Lusitanian chief called Punicus invaded the Roman territory, defeated two Roman governors, and killed their troops. The Romans resolved to send a consul to Hispania, and in order to accelerate the dispatch of aid, "they even made the new consuls enter into office two months and a half before the legal time" (March 15).

Symbols

January's birthstone is the garnet, which represents constancy. Its birth flower is the cottage pink Dianthus caryophyllus, galanthus or traditional carnation. The zodiac signs are Capricorn (until January 19) and Aquarius (January 20 onwards).

Observances This list does not necessarily imply either official status or general observance.

Month-long

Alzheimer's Awareness Month (Canada) Dry January (United Kingdom) National Codependency Awareness Month (United States) National Mentoring Month (United States) National Healthy Weight Awareness Month (United States) Slavery and Human Trafficking Prevention Month (United States) Stalking Awareness Month (United States) Veganuary

Food months in the United States This list does not necessarily imply either official status or general observance.

Be Kind to Food Servers Month (by proclamation, State of Tennessee) California Dried Plum Digestive Health Month Hot Tea Month National Soup Month Oatmeal Month

Non-Gregorian All Baha'i, Islamic, and Jewish observances begin at sundown prior to the date listed, and end at sundown on the date in question.

List of observances set by the Bahá'í calendar List of observances set by the Chinese calendar List of observances set by the Hebrew calendar List of observances set by the Islamic calendar List of observances set by the Solar Hijri calendar

Moveable This list does not necessarily imply either official status or general observance.

See: List of movable Western Christian observances See: List of movable Eastern Christian observances January 2 unless that day is a Sunday, in which case January 3

New Year Holiday (Scotland) First Friday

Children's Day (Bahamas) Second Saturday

Children's Day (Thailand) Second Monday

Birthday of Eugenio María de Hostos (Puerto Rico, United States) Coming of Age Day (Japan) Friday before third Monday

Lee–Jackson Day (Virginia, United States, defunct) Third Friday

International Fetish Day Sunday closest to January 22

National Sanctity of Human Life Day (United States) Third full week of January

Hunt for Happiness Week (International observance) National Non-Smoking Week (Canada) Last full week of January

National School Choice Week (United States) Third Monday

Martin Luther King, Jr. Day (United States) Idaho Human Rights Day (Idaho, United States) Wednesday of the third full week of January

Weedless Wednesday (Canada) Friday between January 19–25

Husband's Day (Iceland) Last Saturday

National Seed Swap Day (United States) Last Sunday

Liberation of Auschwitz Memorial Day (Netherlands) World Leprosy Day Last Monday in January

Bubble Wrap Appreciation Day Fourth Monday

Community Manager Appreciation Day (International observance) National Heroes' Day (Cayman Islands) Monday Closest to January 29

Auckland Anniversary Day

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with January

Start with the simplest possible case. Write down what January claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to January before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about January ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of January

In research: January appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses January in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: January is common in secondary-school and first-year university syllabi. It links to neighbouring topics January, Months, so understanding it makes those chapters shorter.
In everyday life: Look for January outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study January in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what January means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain January out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is January in simple terms?

January is the first month of the year in the Julian and Gregorian calendars. Its length is 31 days.

Why does January matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study January?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on January.