feat(plugin): add timestamp-context plugin

[NoRain211]

Summary

Adds a timestamp-context plugin that injects the current local time (ISO 8601 with timezone offset) into conversation context on every message via a UserPromptSubmit hook.

Motivation

Claude Code includes the date in its system prompt but not the time or timezone. This has been requested multiple times:

• Add Current Date and Time to System prompt #1164 — "Add Current Date and Time to System prompt"
• A date tool should be included by default #2618 — "A date tool should be included by default"
• feat: inject current local time into conversation context by default #23655 — "Inject current local time into conversation context by default"

Until this is built into core, a plugin provides an easy opt-in solution.

What it does

A UserPromptSubmit hook runs a Node.js one-liner that outputs the local time. Since UserPromptSubmit stdout is injected as context, Claude sees the timestamp on every message.

Example context injected:

The current local time is: 2026-02-06T04:39:00-07:00. This is the latest source of truth for time; do not attempt to get the time any other way.

Details

• Zero dependencies — uses only Node.js (already required by Claude Code)
• Auto-detects timezone — uses system locale, no user configuration needed
• Negligible cost — ~120 characters per message

Test plan

• Enable plugin and start a new session
• Send a message and verify Claude receives the timestamp in context
• Confirm timezone offset matches the local system timezone

🤖 Generated with Claude Code