Plain-language guides to how ages, dates and calendars work.
Completed years, Korean age and year age explained with examples, plus the 2023 change in South Korea.
Why 29 February exists, how leaplings are aged, and how birthdays are treated in non-leap years.
A step-by-step guide for exam, job and application cutoffs, with worked examples.
Two simple methods that handle leap years and year boundaries.
Why 1582 skipped ten days and when different countries switched.
How week 1 is defined and why some years have 53 weeks.
The 400-year cycle and the Doomsday rule for finding weekdays in your head.