NCERT Solutions Exploring Society: India and Beyond Chapter 4 How Is Time Measured in History? — LET'S EXPLORE
Book page 63 Updated on2026-09-05
Q1.
Such calculations are simple, but there is a catch. In the Gregorian calendar, there is no ‘year zero’. The year 1 CE follows immediately the year 1 BCE. Draw a simple timeline marking every year from 2 BCE to 2 CE; you will see that because of the absence of a year zero, only 3 years have passed between those two dates.
Answer
Here is that timeline, with every single year marked. There are four year-labels but only three gaps between them — and each gap is one year.
Every year from 2 BCE to 2 CE. Four years are named, three years actually pass — because the calendar jumps from 1 BCE to 1 CE with nothing in between.
Years named: 2 BCE, 1 BCE, 1 CE, 2 CE → 4 labels
Gaps between labels: 3
Years passed from 2 BCE to 2 CE = 3 years
Why there is no year zero: the system was worked out in Europe in the 6th century CE, long before the number zero was in ordinary European use for counting. Counting began at “one”, both forwards and backwards. Ironically, zero as a number had already been developed in India — but it had not yet reached the people who drew up this calendar.
Q2.
So to calculate the number of years between a BCE date and a CE date, you should add them but subtract 1 — in the above case, 2 + 2 – 1 = 3.
Answer
That is the rule for the whole chapter. Write it once and use it every time:
Gap between a BCE date and a CE date = BCE + CE – 1
Check on the example above: 2 + 2 – 1 = 3 ✓
But be careful — the rule only applies when the two dates are on opposite sides of the line. Here are all three cases:
Both dates are …
Rule
Worked example
One BCE, one CE
add, then subtract 1
560 BCE → 2024 CE = 560 + 2024 – 1 = 2,583 years
Both CE
subtract
1828 CE → 1947 CE = 1947 – 1828 = 119 years
Both BCE
subtract (the bigger number is the earlier date)
560 BCE → 320 BCE = 560 – 320 = 240 years
Check it yourself: from 1 BCE to 1 CE the rule gives 1 + 1 – 1 = 1 year, which is right — one year passes between them. Without the “– 1” you would get 2, which would be wrong.
Q3.
Practice a few examples with your classmates. For example, to return to the question about the Buddha, suppose we are now in the year 2024 CE, then the Buddha was born 560 + 2024 – 1 = 2,583 years ago.
Answer
Here is a set of practice sums you can use in class, each one worked out in full. Cover the right-hand column, try them, then check.
Question
Working
Answer
How long from 560 BCE (the Buddha's birth) to 2024 CE?
560 + 2024 – 1
2,583 years
How long from 560 BCE to 2026 CE?
560 + 2026 – 1
2,585 years
How long from 2500 BCE (Indus–Sarasvatī cities) to 2024 CE?
2500 + 2024 – 1
4,523 years
How long from 250 BCE (Aśhoka) to 2024 CE?
250 + 2024 – 1
2,273 years
How long from 560 BCE (Buddha) to 250 BCE (Aśhoka)? Both BCE
560 – 250
310 years
How long from 1947 CE to 2026 CE? Both CE
2026 – 1947
79 years
How long from 323 BCE to 323 CE?
323 + 323 – 1
645 years
A coin is said to be 2,000 years old in 2024 CE. What year was it made?
Y + 2024 – 1 = 2000 → Y = 2000 – 2023 = –23, i.e. the date falls after 1 CE: 2024 – 2000 = 24
24 CE
Try this in class: make two paper strips, one for BCE years and one for CE years, and join them so that “1 BCE” touches “1 CE” with no gap. Slide a marker along and count aloud. Once you have seen that there is no space for a year zero, you will never forget the “– 1”.