Measuring historical time

Detail

What "history" means and why time-keeping matters

• History = the study of the human past. E.H. Carr called it an "unending dialogue between the present and the past" — each generation asks new questions of the same evidence.
• History needs a frame to place events in order. That frame is time.
• Societies across the world opened new eras (counting systems for years) from a big event — the birth of a religious founder, or the start of a king's reign.
• An era is a human choice, not a natural fact. Different societies picked different starting points, so the same year can carry many different numbers.

The Gregorian calendar

• The calendar used worldwide today has 12 months and 365 days in a normal year.
• A leap year of 366 days comes every 4 years, to match the extra quarter-day the earth takes to go round the sun.
• Exception for century years: a year ending in 00 is a leap year only if it divides by 400. So of 1800, 1900 and 2000, only 2000 was a leap year.
• This calendar was brought in by Pope Gregory XIII on 24 February 1582 through the bull Inter gravissimas ("In the Gravest Concern"). [3][4]
• It replaced the Julian calendar, in use since 46 BCE. The Julian year was slightly too long, so the dates of the seasons slipped back nearly one day per century. [3]
• To fix the drift already built up, 10 days were dropped in October 1582 — 4 October was followed by 15 October — pulling the spring equinox back from 11 March to 21 March. [3]
• The 400-year rule is the only real difference from the Julian calendar: 1600 and 2000 were leap years; 1700, 1800 and 1900 were not. [3][4]
• Countries adopted it at different times — Britain and its colonies in 1752, Japan 1873, China 1912, Russia 1918, Greece 1923. [3]

AD/BC becoming CE/BCE

• Years are counted forward and backward from the conventional year of the birth of Jesus.
• Old labels: AD (Anno Domini, "in the year of the Lord") and BC ("Before Christ").
• New labels used in NCERT and in scholarship: CE = Common Era, BCE = Before Common Era.
• The numbers do not change — only the name. 1947 AD = 1947 CE.
• The change was made because the counting system is now used by people of every religion, so a neutral name fits better.
• Example from the scaffold: the Buddha was born about c. 560 BCE.

There is no year zero

• 1 CE comes straight after 1 BCE. There is no year 0 in between.
• So the stretch from 2 BCE to 2 CE is only 3 years, not 4.
• Rule to find "how many years ago": BCE date + CE year − 1.

• For the Buddha's birth: 560 + 2024 − 1 = 2,583 years ago.

• Exam trap: students add without subtracting 1 and get the answer wrong by exactly one year.

Century and millennium — how to count them

• A century = 100 years.
• Counting forward from 1 CE: the 1st century CE = 1–100 CE, so the 21st century = 2001–2100 CE.
• Counting backward from 1 BCE: the 1st century BCE = 100–1 BCE, so the 3rd century BCE = 300–201 BCE.
• Note the direction: in BCE, the bigger number is the earlier year. 300 BCE is older than 201 BCE.
• A millennium = 1,000 years. The 1st millennium BCE = 1000 BCE to 1 BCE.
• Quick method: for a CE year, drop the last two digits and add 1 (1947 → 19 + 1 = 20th century).

Short forms you must know (Class 12 Part 1, Ch 1 "Bricks, Beads and Bones - The Harappan Civilisation" box)

• BP = Before Present — used for very old dates, mostly from science-based dating. Counts back from the present.
• BCE = Before Common Era · CE = Common Era.
• c. = circa, Latin for "about". It warns you the date is approximate, not exact — as in c. 560 BCE.

Timelines

• A timeline puts events in order along a line, oldest first.
• It works even when we have no exact dates. We still know the Buddha came before Jesus, so their order on the line is certain.
• This is useful for early India, where many events have only a rough order, not a year.

Indian calendars running alongside the Gregorian

• Indian calendars are still in daily use next to the Gregorian one.
• The pañchānga is a book of tables of days carrying astronomical data. It is used to predict eclipses, sunrise and sunset times and the dates of festivals. It is still widely used today.
• India also has an official Indian National Calendar, based on the Śaka era, which begins in 78 CE. [2]
• It was adopted by the Government of India from 1957, on the recommendation of the Calendar Reform Committee, and is used alongside the Gregorian calendar for official purposes. [2][5]
• Its first month is Chaitra — 30 days in a normal year, 31 in a leap year; the next five months have 31 days, the rest 30. The year starts the day after the vernal (spring) equinox. [2]
• The Śaka era (78 CE) is the most widely used of all Indian eras. [2]
• Other eras seen in Indian inscriptions and texts include the Vikrama Samvat (58 BCE) — one reason two Indian sources can date the same event with two different year numbers.

Prelims Hooks

• Only 2000 among 1800, 1900 and 2000 was a leap year — century years are leap only if divisible by 400.
• Gregorian calendar introduced by Pope Gregory XIII on 24 February 1582 through the bull Inter gravissimas. [3][4]
• 10 days were dropped in October 1582 — 4 October followed by 15 October. [3]
• Britain and its colonies adopted the Gregorian calendar in 1752; Japan 1873; China 1912; Russia 1918. [3]
• There is no year zero — 1 CE follows 1 BCE directly; 2 BCE to 2 CE = 3 years.
• 21st century = 2001–2100 CE; 3rd century BCE = 300–201 BCE; 1st millennium BCE = 1000 BCE–1 BCE.
• BP = Before Present; c. = circa = approximate.
• Indian National Calendar adopted 1957, based on the Śaka era of 78 CE, first month Chaitra. [2][5]
• Pañchānga = book of day-tables with astronomical data; predicts eclipses, sunrise/sunset and festival dates.
• Buddha's approximate birth c. 560 BCE → 2,583 years before 2024 (560 + 2024 − 1).

Mains Points

• Dating systems are political as well as technical. The shift from AD/BC to CE/BCE keeps the same numbers but removes the Christian label, so a system used by all faiths gets a neutral name. Likewise, India's adoption of the Śaka-era national calendar in 1957 was a statement of national identity as much as a scientific reform. [2][5] Useful in GS-I answers on culture, identity and the making of modern India.
• Every era has an arbitrary starting point. Śaka (78 CE), Vikrama Samvat (58 BCE) and the Christian era all begin from a chosen event. This matters for source criticism: an inscription dated "year 12" is useless until you know which era the mason was counting in — a standard problem in reading Indian epigraphs (Class 12 Part 1, Ch 2 "Kings, Farmers and Towns").
• Relative dating can do real work when absolute dates are missing. Timelines show that the Buddha came before Jesus without either date being fixed. This is the same logic as stratigraphy (reading layers of soil at a dig, oldest at the bottom) in archaeology — order first, exact years later.
• Calendars record scientific skill, not only belief. The pañchānga predicts eclipses and sunrise/sunset times, and the Gregorian reform of 1582 was driven by a measured error in the length of the solar year. [3] Both show societies correcting their calendars against the sky — evidence for the history of Indian astronomy in GS-I "Indian culture" answers.