Add CLAUDE.md documentation for Claude Code

This file provides guidance to future Claude instances working with this repository, including:
- Key development commands
- High-level architecture overview
- Important design patterns and constants
- Development best practices specific to this codebase

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: borkweb

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+StellarWP Dates is a PHP library for WordPress that provides comprehensive date and time utilities. It's forked from The Events Calendar's battle-tested date handling functionality and serves as a community resource from StellarWP.
+
+## Commands
+
+### Development Commands
+```bash
+# Generate documentation from PHPDoc comments
+composer create-docs
+
+# Run static code analysis
+composer test:analysis
+
+# Install dependencies
+composer install
+```
+
+### Testing
+The project uses Codeception for testing. Tests are located in `tests/wpunit/` and require WordPress test environment setup. Test configuration is in `codeception.dist.yml` and `codeception.slic.yml`.
+
+## Architecture
+
+### Core Classes
+- **`Dates`** (src/Dates/Dates.php): Main utility class with 70+ static methods for date operations
+- **`Date_I18n`** (src/Dates/Date_I18n.php): Mutable DateTime extension with WordPress I18n support
+- **`Date_I18n_Immutable`** (src/Dates/Date_I18n_Immutable.php): Immutable version of Date_I18n
+- **`Timezones`** (src/Dates/Timezones.php): Timezone utilities integrated with WordPress
+
+### Key Design Patterns
+1. **All dates are built through `Dates::get()`** - This is the primary entry point for date creation
+2. **Fallback handling** - Methods accept optional fallback values for invalid dates
+3. **WordPress integration** - Deep integration with WordPress timezone and locale systems
+4. **Immutability support** - Both mutable and immutable date objects available
+
+### Important Constants
+The library defines format constants in `Dates.php`:
+- `DBDATEFORMAT` = 'Y-m-d'
+- `DBDATETIMEFORMAT` = 'Y-m-d H:i:s'
+- `DATEONLYFORMAT` = 'F j, Y'
+- `TIMEFORMAT` = 'g:i a'
+
+### Code Quality
+- **PHPStan Level 3** with WordPress-specific rules
+- Configuration in `phpstan.neon.dist`
+- Ignores certain WordPress patterns (func_get_args usage)
+
+## Development Notes
+
+1. **Namespace**: All code under `StellarWP\Dates` namespace
+2. **Installation**: Recommend using Strauss for namespace isolation to avoid conflicts
+3. **Date Building**: Always use `Dates::get()` rather than direct instantiation
+4. **Timezone Handling**: Library automatically falls back to WordPress timezone or UTC
+5. **Testing**: Requires WordPress test environment setup for full test suite execution