Months of the Year: Names, Lengths, and Origins
Last reviewed on May 4, 2026
The Gregorian calendar — the one in civil use across most of the world — has 12 months of unequal length. The names come from a mix of Roman gods, Roman emperors, and Latin numerals that no longer match the position of the month in the year. This page covers each month: where the name came from, how many days it has, the Northern Hemisphere season it falls in, the traditional birthstone and birth flower, and a link to every month's printable calendar in any year between 2025 and 2045.
How the year ended up with 12 unequal months
The earliest Roman calendar had 10 months and started in March; January and February were added later. That's why September, October, November, and December — from septem (7), octo (8), novem (9), and decem (10) — are now the 9th, 10th, 11th, and 12th months. The shift left the names two positions out of step, and they've stayed that way ever since. The lengths (28, 29, 30, or 31 days) come from the Julian reform of 46 BCE, with one tweak in the Augustan period and a small refinement in the Gregorian reform of 1582 to keep the calendar aligned with the seasons.
The 12 months
January — 31 days
Named after Janus, the Roman god of beginnings, transitions, gates, and doorways. Janus was depicted with two faces, one looking forward and one looking back — fitting for the month that separates the old year from the new. January is the first month of the year in the Gregorian calendar, the second-coldest month in the Northern Hemisphere, and the month of New Year's Day and Martin Luther King Jr. Day in the United States.
Birthstone: garnet. Birth flower: carnation or snowdrop. Zodiac signs: Capricorn until about the 19th, then Aquarius. See the January 2026 calendar.
February — 28 days (29 in leap years)
Named after Februa, an ancient Roman purification festival held in mid-February. February is the shortest month and the only one whose length changes from year to year — see the leap years page for the rule. Holidays in February include Valentine's Day (February 14) and Presidents Day (third Monday).
Birthstone: amethyst. Birth flower: violet or primrose. Zodiac signs: Aquarius, then Pisces. See the February 2026 calendar.
March — 31 days
Named after Mars, the Roman god of war. In the original Roman calendar, March was the first month of the year — which is why some legal and accounting traditions still treat the start of spring as the start of a "year." March contains the spring equinox in the Northern Hemisphere (around March 20), the start of Daylight Saving Time in the US (second Sunday), and St. Patrick's Day (March 17).
Birthstone: aquamarine. Birth flower: daffodil. Zodiac signs: Pisces, then Aries. See the March 2026 calendar.
April — 30 days
The origin of "April" is debated. The most accepted source is the Latin aperire, "to open," referring to spring buds opening. April contains April Fools' Day (April 1), Earth Day (April 22), and the most common dates for Western Easter (which moves between March 22 and April 25 — see the Easter dates page).
Birthstone: diamond. Birth flower: daisy or sweet pea. Zodiac signs: Aries, then Taurus. See the April 2026 calendar.
May — 31 days
Named after Maia, a Roman earth goddess associated with growth and fertility. May contains the May Day labour holiday (May 1, observed in most countries except the US and Canada), Mother's Day in the US (second Sunday), Cinco de Mayo (May 5), and Memorial Day (last Monday).
Birthstone: emerald. Birth flower: lily of the valley or hawthorn. Zodiac signs: Taurus, then Gemini. See the May 2026 calendar.
June — 30 days
Named after Juno, Roman goddess of marriage and queen of the gods — which may be where the association of June with weddings comes from. June contains the summer solstice in the Northern Hemisphere (around June 20–21), Father's Day in the US (third Sunday), and Juneteenth (June 19).
Birthstone: pearl. Birth flower: rose or honeysuckle. Zodiac signs: Gemini, then Cancer. See the June 2026 calendar.
July — 31 days
Named after Julius Caesar, who reformed the calendar in 46 BCE and was born in this month (originally called Quintilis, "fifth"). July contains Independence Day in the US (July 4), Canada Day (July 1), and Bastille Day in France (July 14). It is typically the warmest month in the Northern Hemisphere.
Birthstone: ruby. Birth flower: larkspur or water lily. Zodiac signs: Cancer, then Leo. See the July 2026 calendar.
August — 31 days
Named after Augustus Caesar, the first Roman emperor (originally Sextilis, "sixth"). August has 31 days because, the story goes, Augustus did not want his namesake month to be shorter than Julius Caesar's. The shift required moving a day from February, which is one of the explanations offered for why February is so short. August is the only month with no US federal holiday at all.
Birthstone: peridot. Birth flower: gladiolus or poppy. Zodiac signs: Leo, then Virgo. See the August 2026 calendar.
September — 30 days
From Latin septem, "seven" — September was the seventh month in the original Roman calendar, which started in March. September contains Labor Day in the US (first Monday) and the autumnal equinox in the Northern Hemisphere (around September 22–23). The school year starts in September in most of the Northern Hemisphere.
Birthstone: sapphire. Birth flower: aster or morning glory. Zodiac signs: Virgo, then Libra. See the September 2026 calendar.
October — 31 days
From Latin octo, "eight." October contains Columbus Day / Indigenous Peoples' Day in the US (second Monday) and Halloween (October 31). The fall foliage season in the temperate Northern Hemisphere usually peaks in October.
Birthstone: opal or tourmaline. Birth flower: marigold or cosmos. Zodiac signs: Libra, then Scorpio. See the October 2026 calendar.
November — 30 days
From Latin novem, "nine." November contains Veterans Day in the US (November 11), Thanksgiving (fourth Thursday), and the end of Daylight Saving Time in the US (first Sunday). It is statistically the shortest working-day month in the US because of how the holidays cluster — see working days vs calendar days.
Birthstone: topaz or citrine. Birth flower: chrysanthemum. Zodiac signs: Scorpio, then Sagittarius. See the November 2026 calendar.
December — 31 days
From Latin decem, "ten." December contains Christmas Day (December 25), New Year's Eve (December 31), the winter solstice in the Northern Hemisphere (around December 21), and Hanukkah in most years. It is the last month of the calendar year and one of the shortest working-day months because of the holiday cluster.
Birthstone: turquoise, tanzanite, or zircon. Birth flower: narcissus or holly. Zodiac signs: Sagittarius, then Capricorn. See the December 2026 calendar.
Day counts at a glance
| Month | Days | Quarter | Northern season |
|---|---|---|---|
| January | 31 | Q1 | Winter |
| February | 28 / 29 | Q1 | Winter |
| March | 31 | Q1 | Winter / Spring |
| April | 30 | Q2 | Spring |
| May | 31 | Q2 | Spring |
| June | 30 | Q2 | Spring / Summer |
| July | 31 | Q3 | Summer |
| August | 31 | Q3 | Summer |
| September | 30 | Q3 | Summer / Autumn |
| October | 31 | Q4 | Autumn |
| November | 30 | Q4 | Autumn |
| December | 31 | Q4 | Autumn / Winter |
The "knuckle" memory aid
Make a fist. Starting at the index-finger knuckle, count out the months — knuckle, valley, knuckle, valley — across both hands. Knuckles are 31-day months; valleys are 30-day months. February (the third position) is the only exception. The trick works because seven of the twelve months are 31-day months and they cluster at the boundaries of the year.
Common mistakes
- Reading "Sept-, Oct-, Nov-, Dec-" as 9, 10, 11, 12. The roots are 7, 8, 9, 10 — a vestige of the older Roman calendar.
- Assuming February always has 28 days. It has 29 in leap years.
- Assuming "August" comes from a Latin adjective. It comes from a personal name — Augustus.
- Assigning April Easter dates as if Easter is always in April. It can fall as early as March 22 (in the Western tradition) or as late as April 25; see Easter dates.
Related
- Days of the week — origins of the seven weekday names.
- 2026 monthly calendars — pick any month.
- 2026 US federal holidays — the major dates above in calendar form.
- Leap years — why February's length changes.