Days Until 18 (Legal Age)

How many days until the driving licence, the enlistment date, the point where a contract no longer needs a guardian's signature? Counting that on a calendar is tedious because months have different lengths and leap years wreck any mental arithmetic. Here you fill in a birth date, fill in a reference date, and get the number of days still left before the eighteenth birthday.

The math adds 18 years to the day and month of birth and measures the plain day difference to the reference date. Someone born on 2010-01-01 turns 18 on 2028-01-01, which was 600 days away on 2026-05-11. Two details: if the reference date is on or after the birthday, the result reads Já maior, Portuguese for already of age; and a 29 February birth landing on a non-leap year rolls forward, so 2008-02-29 plus 18 years becomes 2026-03-01 by the convention used here.

The field labelled Hoje, meaning today, does not fill itself with the current date. It loads a fixed value, so change it before reading the number or the countdown will be wrong. The output is a day count, not the birthday date itself; add 18 years on a calendar if you need the date. The age is hardwired at 18, so 16 or 21 are out of reach. Remember that each right has its own rule anyway, such as optional voting from 16 in Brazil. It all runs in your browser.