Century to Month

The 1920s confidently predicted personal autogyros (helicopter-planes) would replace cars within decades — they never became practical for commuters. Pneumatic tube mail was expected to connect every home; it peaked in the 1930s and vanished. Radium-infused products (water, toothpaste, suppositories) were marketed as health miracles until people started dying. Moving sidewalks, demonstrated at the 1900 Paris Exposition, were expected to replace urban walking. Airships were the "future of travel" until the Hindenburg (1937). Meanwhile, technologies nobody hyped — antibiotics, containerised shipping, transistors — quietly reshaped civilisation without fanfare.

Carbon-14 dating (radiocarbon dating) is reliable for organic material up to ~50,000 years (roughly 500 centuries). Precision is typically ±40–200 years for samples from the last 2,000 years, improving to ±centuries for older samples. Calibration against dendrochronology (tree rings) sharpens accuracy significantly. The method measures the decay of ¹⁴C (half-life 5,730 years) — after ~8 half-lives (46,240 years), too little ¹⁴C remains to measure reliably.

The Westinghouse generators installed at Niagara Falls in 1895 ran until 2006 — 111 years. Many Victorian-era water mains and sewer systems in London (built 1858–1875) are still in service. Stradivarius violins from 1700 are still played. The Antikythera mechanism (ancient Greek astronomical computer, ~87 BCE) still demonstrates correct gear ratios. Some Japanese Buddhist temples have been maintained continuously for 14 centuries.

IPCC projections (2021) estimate 0.3–1.0 m of sea level rise by 2100 (0–1 century from now) under moderate to high emissions scenarios. Under worst-case scenarios involving ice sheet instability, multi-meter rise within 1–2 centuries is possible. The last time CO₂ was at current levels (around 3 million years ago), sea levels were 15–25 m higher — though the adjustment to that equilibrium takes centuries to millennia.

The University of Bologna (founded 1088) is the oldest continuously operating university — now over 9 centuries old. The Papacy has continued as an institution for approximately 20 centuries. The oldest continuously operating business is Kongo Gumi, a Japanese temple builder founded in 578 CE — 14+ centuries, though it was absorbed into a larger company in 2006. The British Crown Jewels include items spanning 10 centuries of continuous use.

The Roman calendar originally had 10 months (March through December), leaving winter uncounted. January and February were added by King Numa Pompilius around 713 BCE to cover winter. To keep the total at 355 days (a lunar year), February got the leftover days — 28. Julius Caesar's 365-day calendar reform kept February shortest. The "30 days hath September" mnemonic reflects decisions made by Roman senators to honor Augustus and Julius Caesar with 31-day months, robbing days from February.

Four weeks are exactly 28 days. The selected month in this converter is 365/12 days, approximately 30.4167 days, so it is not four weeks. Actual Gregorian calendar months have 28–31 days; February in a common year has exactly four weeks. Use calendar dates when the actual month length matters.

The irregular distribution (JMMJSND = 31 days; AJJN = 30 days; Feb = 28/29) comes from Julius Caesar's calendar reform (45 BCE) and later Augustan adjustments. Caesar gave odd months 31 days and even months 30 (with February 29/30). Augustus then renamed "Sextilis" after himself and extended it to 31 days to match Julius's month — taking a day from February. The resulting pattern has persisted for 2,000 years.

A sidereal month is the time for the Moon to orbit Earth relative to distant stars: 27.32 days. A synodic month is the time between identical lunar phases (new moon to new moon): 29.53 days. The synodic month is longer because Earth moves along its orbit — the Moon must travel further to reach the same phase angle relative to the Sun. Islamic and Hebrew lunar calendars are based on the 29.53-day synodic month.

Yes. The converter defines a month as exactly 2,628,000 seconds and a year as exactly 31,536,000 seconds, so 12 months equal one 365-day year. This is a fixed-duration convention, not a lunar-month average or a calendar calculation that accounts for leap days.