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The stories behind the numbers: how they are worked out, where the data comes from and how to read them. Add your birthday and every guide below shows what it means for you.

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36·6·18Time lived · 9 minHow to calculate your exact ageThe borrowing method by hand, the leap-day traps, and why two calculators can disagree by a day. 29Time lived · 9 minLeap years explainedWhy 2000 was a leap year but 1900 was not, where the extra day came from, and what it means if you were born on 29 February. MTWTFSSTime lived · 10 minWhat day of the week was I born?The doomsday method, step by step, with the anchor days, the memory dates and four worked examples. Peers & the world · 10 minGenerations by birth yearThe birth-year ranges, why sources disagree, what a cusper is, and how big each generation really is. Planets & cosmos · 9 minDog years explainedHow fast dogs really age, why size changes everything, and what the newest research says about the first two years. Planets & cosmos · 8 minCat years explainedThe fast first two years, the steady four-a-year rule after that, and the six life stages vets use. youPeers & the world · 10 minLife expectancy explainedPeriod and cohort figures, why your expected age rises as you get older, and what the average can and cannot tell you. Planets & cosmos · 9 minHow long is a year on each planet?Orbit times and day lengths for all eight planets, why Venus has a day longer than its year, and how planet ages work. 67Looking ahead · 9 minFull retirement age by birth yearYour full retirement age, what claiming at 62 or 70 does to the benefit, and the first-of-the-month rule that catches people out. $Peers & the world · 9 minWhat a dollar was worth the year you were bornHow the Consumer Price Index works, the simple formula for converting old prices, and a decade-by-decade table. 
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