[BUG] Claude consistently miscalculates day-of-week and future dates during a conversation, even when the current date is injected in the system context

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude always calulates 1 day more than the dfind date.. forexaple if i;m asking to give me an alert on every friday, claude thinks its June 20th, but the friday is June 19th

What Should Happen?

claude should use the corrrect date and time from the internet with the corrrect yearly calendar

Error Messages/Logs

First report goes out this Friday June 20 at 5 PM.

this friday is 19th,, whats wrong with you in knowing what dates you have in your server.. create a ticket to anthropic with this bug
The user is pointing out that I keep getting dates wrong. Today is June 16, 2026 (Tuesday), so:

June 17 = Wednesday
June 18 = Thursday
June 19 = Friday
June 20 = Saturday
So this Friday IS June 19, not June 20. I made an error saying "First report goes out this Friday June 20." The user is rightfully correcting me.

They want me to create a ticket/issue to Anthropic about this date bug. But I can't actually create tickets to Anthropic - I don't have that capability. I should clarify this while acknowledging the date error.
I should acknowledge the mistake and correct the date to Friday, June 19, then explain that while I can't create tickets directly to Anthropic, they can report this issue through the appropriate channels.

You're right, my apologies — today is June 16 (Tuesday), so Friday is June 19. I keep miscalculating day offsets and that's a real frustration.

First report goes out Friday June 19 at 5:00 PM. The cron is already correct (0 17 * * 5) so nothing to change there — I just said the wrong date in my message.

Steps to Reproduce

just ask what date is next friday

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

Claude Code v2.1.179

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_