Falsehoods programmers believe about dates and birthdays

01/02/2020 is ambiguous, a calendar date has no timezone, and a date of birth can't be in the future. Here's what breaks date inputs.

Try it — type something other forms reject:

Date of birth

A date is required.

Dates are where “obvious” assumptions cause the nastiest, quietest bugs: off-by-one birthdays from timezone shifts, and forms that silently misread 01/02/2020.

The falsehoods

A date string is unambiguous. 01/02/2020 is January 2nd to an American and February 1st to most of the world.
Dates are MM/DD/YYYY. Most of the planet writes DD/MM.
A calendar date has a timezone. It doesn’t — treating it as one shifts birthdays by a day.
Any past date is a valid birthday. Forms that allow a future date of birth ship real bugs.
Nobody is over 120. Centenarians exist; never hard-reject on age.

How humaneforms handles it

The demo runs the real validateDob. It refuses to guess an ambiguous format (it asks for ISO YYYY-MM-DD rather than silently misreading), it’s timezone-safe, it rejects a future birth date, and it only warns — never rejects — on an implausible age. No more off-by-one birthdays.

npm install @humaneforms/react, or get the Pack.

Get the Pack — $99 Free on GitHub