BrainiLab Academy · History
Make sense of years and calendars
Centuries, leap years and eleven missing days: untangle the oddities of our calendar, one short read at a time.
Start learning →
What you’ll explore
Start with a week and a month. Then zoom out to centuries, test the rules for leap years and discover why a real calendar once skipped eleven date labels.
One discovery at a time
Your lessons, step by step
- 1
Read →2 min read · Quick quiz
Days, weeks, months and years explained
Separate the weekday cycle from month and year lengths.
Ready when you are - 2Read →
2 min read · Quick quiz
How do you work out a year’s century?
Put years into boxes of one hundred.
Ready when you are - 3
Read →3 min read · Quick quiz
Why isn't 2100 a leap year?
Find out why February sometimes gets an extra day.
Ready when you are - 4
Read →2 min read · Quick quiz
Why did Britain skip 11 days in 1752?
Discover how a date jumped forward while life went on as usual.
Ready when you are
A few words worth knowing
- Century
- A group of one hundred years.
- Leap day
- The extra day, 29 February, added in a leap year.
- Calendar
- A system for giving dates to days, months and years.
Curious to dig deeper?
- US Naval Observatory — The 21st century and 3rd millennium
- NASA — Calendars and their History
- NASA Space Place — What Is a Leap Year?
- UK legislation — Calendar (New Style) Act 1750, sections 1–2
- Royal Museums Greenwich — Leap years and the 1752 calendar change
Follow the sources, explore a little further, or tell us if something needs a correction. Suggest a correction.