Simon Willison’s Weblog

A Zoned Defense. Using JavaScript’s date.getTimezoneOffset() to detect the user’s timezone and stash it in a cookie.

Posted 20th March 2007 at 9:51 am

Recent articles

Video: Building a tool to copy-paste share terminal sessions using Claude Code for web - 23rd October 2025
Dane Stuckey (OpenAI CISO) on prompt injection risks for ChatGPT Atlas - 22nd October 2025
Living dangerously with Claude - 22nd October 2025

javascript 723 timezones 15

Monthly briefing

Sponsor me for $10/month and get a curated email digest of the month's most important LLM developments.

Pay me to send you less!

Sponsor & subscribe