The chronology desk · free web companion
What century is this BCE date?
201 BCE is in the 3rd century. The following year, 200 BCE, begins the 2nd. Make the backwards-counting years click.
Find a year’s century ↓Place a year on the shelf.
Enter a whole year from 1 to 9999. BCE uses the same year numbers as BC; CE uses the same year numbers as AD.
3rd century BCE
300–201 BCE. 201 BCE is the last year in this century.
Time runs left to right. Position 100 of 100.
The rule
Count the first hundred.
The 1st century CE runs from 1 CE to 100 CE. The 2nd runs from 101 to 200. For a positive year number, divide by 100 and round up: 1900 ÷ 100 = 19, while 1901 ÷ 100 = 19.01, rounded up to 20.
For BCE, the century number uses the same calculation, but time moves toward smaller year numbers. The 2nd century BCE runs from 200 BCE through 101 BCE. Then the 1st century BCE runs from 100 BCE through 1 BCE.
There is no year zero in this historical BCE/CE convention: 1 BCE is followed by 1 CE. Astronomical year numbering is a different system and is not used here.
Boundary reference
| Century | First → last year |
|---|---|
| 2nd BCE | 200 → 101 BCE |
| 1st BCE | 100 → 1 BCE |
| 1st CE | 1 → 100 CE |
| 20th CE | 1901 → 2000 CE |
| 21st CE | 2001 → 2100 CE |
“The 1900s” usually means 1900–1999. That is not the same range as the 20th century, 1901–2000.
Four-pair chronology challenge
Which date comes first?
Pick the earlier date in each pair. After each choice, see how the year numbers and century boundaries fit together.
Round 1 of 4
The link starts these four pairs again without revealing answers or scores.
Ready to investigate a real event? PastRush includes six free cases, including Pompeii and the Rosetta Stone. Six more cases are available with an optional one-time purchase.
Investigate a case in PastRush on iPhoneWhat this tool can tell you
It places an exact year into an ordinal century. It does not determine whether a historical event’s date is certain, resolve a disputed chronology or convert between calendars. If a source says “circa 200 BCE,” preserve that uncertainty rather than turning it into a precise date.
Keep investigating
Dates are only one part of a case. Try six primary-source evidence challenges to practise separating what a source supports from what it leaves unknown.
Working with recent dates? Compare CE centuries with named decades in the century and decade practice desk.
For a different history skill, explore the resized map scale lab.
Across the era boundary
Years between BCE and CE dates
Compare the starts of two numbered years. In this historical convention, 1 BCE is followed immediately by 1 CE: the gap is one year, not two. There is no year zero.
Whole years 1–9999 only. This is a year-number comparison, not an exact elapsed-time calculator for events with unknown months or days.
Why subtract one across BCE and CE?
Walk through the boundary: 2 BCE → 1 BCE → 1 CE → 2 CE. Those four labels have three one-year gaps between them. For dates on opposite sides, add the two positive year numbers and subtract one. For dates in the same era, subtract the smaller year number from the larger.
For example, the starts of 10 BCE and 10 CE are 19 years apart. Reversing A and B keeps that distance, but changes which date is earlier. If both entries name the same year in the same era, the year-start gap is zero.
Keep the precision of your source
A source giving only a year does not tell you the month or day. Two events labelled 100 CE and 101 CE could be days apart or nearly two years apart. Use this tool to understand the year labels; do not turn them into an exact event duration. Preserve words such as “about,” “before” and “after” when a source uses them.
From dates to detective work
Investigate the history behind the timeline.
PastRush: History Detective offers chronology challenges, labelled exhibits and explanations. Start with six free investigations. An optional, one-time Founder Lifetime purchase unlocks cases 7–12 and additional content.
Explore PastRush on the App Store →iPhone and iPad · iOS 18 or later · Free with in-app purchases. Check your storefront for the current price. This independent web exercise is a companion, not an app screenshot or a claim that this calculator is inside the app.