Understanding Historical Time

Before we dive into the actual events of history, let’s first learn how to read time in history.

History is not just what happened, but also when it happened. And to know when, we must understand how time is measured—in centuries, millennia, and using systems like BCE and CE.

Let’s understand this:

📅 The Calendar We Use: Gregorian Calendar

Today, almost the entire world uses the Gregorian calendar. This is the calendar you see on your phone or wall—even your exam date is set by this calendar!

It is based on:

The conventional year of birth of Jesus Christ.

This point becomes the zero point or central reference point of historical time in this calendar.

🔁 What is CE and BCE?

Now here comes a neutral, non-religious way of labeling historical years:

Term	Meaning	Direction
CE	Common Era	Years after the birth of Christ
BCE	Before Common Era	Years before the birth of Christ

Example:

• 500 BCE means 500 years before Jesus Christ.
• 2025 CE means 2025 years after Jesus Christ.

This format (BCE/CE) is widely used in secular and academic history writing, including in UPSC books and NCERTs.

📊 What is a Timeline?

A timeline is like a horizontal number line showing historical events in order.

It helps you:

• Understand sequence (what came before what)
• Understand distance (how many years between events)

🕐 Centuries and Millennia: How to Read Them Correctly

Let’s now learn how historians divide time:

📍 Century = 100 years

• 1st Century CE = 1 CE to 100 CE
• 21st Century CE = 2001 CE to 2100 CE (we’re in it now!)
• 1st Century BCE = 100 BCE to 1 BCE
• 3rd Century BCE = 300 BCE to 201 BCE

NOTE: The century number is always one more than the starting digits.
So, year 2026 is part of the 21st century, not 20th.

📍 Millennium = 1000 years

• 1st Millennium CE = 1 CE to 1000 CE
• 3rd Millennium CE = 2001 CE to 3000 CE
• 1st Millennium BCE = 1000 BCE to 1 BCE
• 8th Millennium BCE = 8000 BCE to 7001 BCE

🔄 Converting BCE to “Years Ago”

This is a very common trick in prelims and PYQs.

To convert BCE into “how many years ago?”, simply add 2000 to the BCE date.
This is because we are currently (roughly) in the year 2000+ CE.

📌 Examples:

• 10,000 BCE = 10,000 + 2000 = 12,000 years ago
• Mesolithic Period began around 10,000 BCE, so it began 12,000 years ago

This is very helpful for understanding prehistoric periods like Paleolithic, Mesolithic, Neolithic, etc.

🧾 Important Abbreviations for UPSC

Abbreviation	Full Form	Meaning
MYA / mya	Million Years Ago	Used for pre-human and early human history
BP	Before Present	Used in archaeology; “Present” = 1950
BCE	Before Common Era	Before year 0
CE	Common Era	After year 0
c.	Circa (Latin)	Means “approximately” (used when the exact date is uncertain)

e.g., c. 1500 BCE means “around 1500 BCE”