Guides & explainers
Short, practical reads on age, dates and time — the ideas behind the calculators, explained in plain language.
Working out your age
How to Calculate Age Correctly (Step by Step)
The simple method behind age calculation, the leap-year traps to avoid, and how to do it by hand or instantly online.
AgeHow Old Am I If I Was Born in a Given Year?
Work out your age from just your birth year, see ages for popular birth years in 2026, and learn why the month matters.
HealthChronological Age vs Biological Age
What each number really measures, why they drift apart, and what the science says you can actually change.
ParentingHow Old Is My Baby in Weeks and Months?
Why newborn age is counted in weeks then months, how the milestones line up, and how to work it out at a glance.
Birthdays & countdowns
What Day of the Week Was I Born On?
How to find the weekday of any birth date, the simple trick behind it, and what your birth day says (and doesn’t).
BirthdayWhen Is My Half Birthday? How to Find It
What a half birthday is, how to calculate the exact date six months from your birthday, and why people celebrate it.
PlanningWhen Will I Turn 18, 21 or Any Age?
Find the exact date you’ll reach a milestone age like 18 or 21, and how to count down to it from today.
PlanningHow to Count the Days Until Any Date
A practical guide to counting down to birthdays, holidays, deadlines and events — and the easy way to get it exact.
CountdownHow Many Days Until Christmas? Counting Down Any Holiday
How to count down to Christmas and any other holiday accurately, plus the quickest way to get the exact number of days.
Calendar & dates
Leap Years Explained: Why February Has 29 Days
The simple rule behind leap years, the century exception almost everyone forgets, and how it keeps our calendar in sync.
CalendarBorn on February 29: How Leap Day Birthdays Work
How leaplings count their age and birthdays, when they legally turn 18 or 21, and how often a ‘real’ birthday comes around.
Culture & fun facts
How Age Is Calculated Around the World
Western, East Asian and lunar age systems explained — why your age can differ by up to two years depending on where you are.
CultureWhat Generation Am I? Birth Years for Each Generation
Boomers, Gen X, Millennials, Gen Z and Gen Alpha — the birth-year ranges for each generation and why the edges are fuzzy.
BirthdayYour Zodiac Sign and Birthstone by Birth Date
The date ranges for every star sign and the birthstone for each month — a quick reference by your date of birth.
Money & practical
Age Last vs Age Nearest vs Age Next: How Insurers Calculate Your Age
The three age bases life insurers use, why your insurance age can be a year higher than your real age, and the date it changes.
RelationshipsCouple Age Difference: Combined Age, Gaps and the “Double Age” Myth
How to work out a couple’s combined age and exact age gap — and why one partner being “double” the other’s age happens only once, ever.
Why these guides exist
Calculating age and dates seems simple until you hit the edge cases — leap years, months of different lengths, the way different cultures count age. These guides unpack the details so the numbers our calculators give you always make sense. They’re free to read, with no signup, and updated as needed.