How to Plan Backwards From a Deadline
Backwards planning starts at the deadline and works back, so you know the real start date. The method step by step, with buffers and a worked example.
Dates & Time
How to Calculate Working Days (Excluding Weekends and Holidays)
Working days are total days minus weekends and public holidays. The counting method by hand, the NETWORKDAYS function, and how weekends differ by country.
Korean Age, Lunar Age, and Other Age Systems Explained
Korean age adds a year at birth and another every New Year, so it runs 1-2 years ahead of international age. How the main age systems differ, with examples.
Dates & Time
What Day of the Week Were You Born?
What day of the week were you born? Use an age calculator, or the Doomsday algorithm by hand. Includes a worked example and century anchor days.
Dates & Time
How Many Weeks Are in a Year (and a Month)?
How many weeks are in a year? 52 weeks plus 1 day (2 in a leap year). Learn why, when a year has 53 weeks, and how many weeks are in a month.
Dates & Time
How to Calculate Business Days Between Dates
How to calculate business days between dates: subtract weekends and public holidays from the total. Includes a worked example and a quick estimate.
Dates & Time
How to Calculate Age From Date of Birth
Year subtraction gets age wrong half the time. The correct method, months-and-days, leap-year birthdays, and other age systems.
Dates & Time
How to Calculate Days Between Two Dates
Subtract the dates, mind the leap day, and decide inclusive vs exclusive counting – the source of most off-by-one errors.
Dates & Time
Countdown Timers: How to Count Down to Any Event
How a countdown works, where it helps, the deadline psychology, and the time-zone catch on shared countdowns.
Dates & Time
How to Convert Time Zones (UTC, GMT, and Offsets)
Convert through UTC every time, mind half-hour zones, and watch the daylight-saving trap that changes the gap between cities.