Guides

Dates and time, explained

Clear, practical guides to the calendar questions people ask every day, each linked to a free calculator so you can try it straight away.

Counting days

Counting days · 4 min read How to count the days between two dates (without mistakes) A simple, reliable method for counting the days between any two dates, including month lengths, leap years, and whether to include the start and end date. Counting days · 4 min read How to count 30, 60 and 90-day deadlines correctly What "within 30 days" really means, whether today counts, what happens on weekends, and how to find the date 30, 60 or 90 days from today. Counting days · 3 min read How to calculate business days (with and without holidays) What counts as a business day, a fast way to count working days between dates, how holidays change it, and how to do it in Excel or Sheets. Counting days · 3 min read How to calculate your exact age in years, months and days A step-by-step way to work out exact age in years, months and days, leap-day birthdays, age in days or weeks, and generation ranges.

Calendars

Calendars · 3 min read Week numbers explained: how ISO weeks work (and why some years have 53) How ISO 8601 week numbers work, why week 1 can start in December, why some years have 53 weeks, and how the US system differs. Calendars · 3 min read How leap years work: the rule, the history and the exceptions Why we add February 29, the full leap year rule with the century exception, why 2000 was a leap year but 2100 won't be, and leap-day birthdays. Calendars · 3 min read Moon phases explained: why the moon changes shape What causes the eight phases of the moon, how long a lunar cycle lasts, what a Blue Moon really is, and the traditional names for each month's full moon.

Holidays

Holidays · 3 min read Why does Easter change every year? The date rule explained Easter can fall from March 22 to April 25. The rule behind the date, why Orthodox Easter often differs, and how Lent and Good Friday follow. Holidays · 3 min read Why Thanksgiving, Memorial Day and Labor Day move every year Why holidays like Thanksgiving and Memorial Day move each year, the laws behind them, and the earliest and latest dates each can fall on. Holidays · 3 min read Why Ramadan, Diwali, Hanukkah and Chinese New Year move every year How the Islamic, Hebrew, Hindu and Chinese calendars work, and why Ramadan, Diwali, Hanukkah and Chinese New Year move every year.

Time zones

Time zones · 3 min read Daylight saving time explained: when the clocks change and why When daylight saving time starts and ends in the US and Europe, which places don't change clocks, and the history behind "spring forward". Time zones · 3 min read Time zones explained: EST, PST, GMT, UTC and IST made simple What UTC and GMT mean, US time zones and their offsets, how daylight saving changes them, and an easy way to convert times between countries.

Money and work

Money and work · 3 min read Biweekly vs semi-monthly pay: what's the difference? Biweekly pay means 26 paychecks a year; semi-monthly means 24. How they differ, three-paycheck months, budgeting, and 27-payday years. Money and work · 2 min read Fiscal year vs calendar year: quarters and year-ends explained What a fiscal year is, how quarters work, and when the fiscal year starts for the US, UK, Australia, India, Pakistan and major companies.

Planning

Planning · 3 min read How to plan a big event with a countdown (weddings, trips, exams) Use a countdown and backward planning for a wedding, trip, exam or launch, with sample timelines and checklists to avoid the last-minute rush.