feat: add Google Calendar support

CLAUDE.md

@@ -7,50 +7,53 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 ```bash
 go build -o gsuite .              # Build binary
 ./gsuite --help                   # Run locally
+go test ./... -race               # Run all tests
 ```
 
 Version is injected at build time via ldflags targeting `cmd.Version`. GoReleaser handles this for releases; for local dev builds, version will show "dev".
 
-No tests exist yet. No linter is configured.
-
 ## Architecture
 
-This is a Go CLI tool using Cobra for Gmail operations via Google service account with domain-wide delegation.
+This is a Go CLI tool using Cobra for Google Workspace operations (Gmail and Calendar) via OAuth2 PKCE authentication.
 
 **Entry point:** `main.go` → `cmd.Execute()`
 
 **Three packages:**
 - `main` — just calls `cmd.Execute()`
 - `cmd` — all Cobra commands and CLI logic
-- `internal/auth` — service account authentication and Gmail service creation
+- `internal/auth` — OAuth2 PKCE authentication, Gmail and Calendar service creation
 
 ### Command Structure
 
-Root command defines persistent flags (`--credentials-file`, `--user`, `--format`, `--verbose`) and exposes getter functions (`GetCredentialsFile()`, `GetUserEmail()`, `GetOutputFormat()`, `GetVerbose()`) used by all subcommands.
+Root command defines persistent flags (`--account`, `--format`, `--verbose`) and exposes getter functions (`GetAccountEmail()`, `GetOutputFormat()`, `GetVerbose()`) used by all subcommands.
+
+Subcommands: `messages`, `threads`, `labels`, `drafts`, `send`, `search`, `calendar`, `whoami`, `version`, `login`, `logout`, `accounts`. Parent commands like `messages` and `calendar` have nested subcommands.
 
-Subcommands: `messages`, `threads`, `labels`, `drafts`, `send`, `search`, `whoami`, `version`. Parent commands like `messages` have nested subcommands (`list`, `get`, `modify`, `get-attachment`).
+Calendar commands: `list`, `get`, `create`, `update`, `delete`, `respond`, `today`, `week`, `calendars`.
 
 ### Command Pattern
 
 Every command function follows this flow:
 1. Get global flags via getter functions from `root.go`
-2. Build `auth.Config` struct
-3. Call `auth.NewGmailService()` to get authenticated client
-4. Execute Gmail API calls
-5. Output as text (default) or JSON based on `--format` flag
+2. Call `auth.NewGmailService()` or `auth.NewCalendarService()` to get authenticated client
+3. Execute API calls
+4. Output as text (default) or JSON based on `--format` flag
 
 ### Authentication Flow
 
 `internal/auth` handles credential loading with this priority:
-1. `--credentials-file` flag
-2. `GOOGLE_CREDENTIALS` env var (raw JSON)
-3. `GOOGLE_APPLICATION_CREDENTIALS` env var (file path)
+1. `GOOGLE_CREDENTIALS` env var (raw JSON)
+2. `GOOGLE_APPLICATION_CREDENTIALS` env var (file path)
 
-Uses JWT config with `gmail.GmailModifyScope`, sets `Subject` to the `--user` email for domain-wide delegation. All API calls use "me" which resolves to the impersonated user.
+Uses OAuth2 PKCE flow with scopes: `gmail.GmailModifyScope`, `calendar.CalendarEventsScope`, `calendar.CalendarReadonlyScope`. Shared auth logic is in `newAuthenticatedClient()` which both `NewGmailService()` and `NewCalendarService()` use.
 
 ### Output Formatting
 
-All commands support `--format text` (default) and `--format json`. JSON output uses inline struct types with `json` tags defined within each command's run function. The shared `outputJSON()` helper in `root.go` handles marshaling.
+All commands support `--format text` (default) and `--format json`. JSON output uses inline struct types with `json` tags defined within each command's run function (never `omitempty`). The shared `outputJSON()` helper in `root.go` handles marshaling.
+
+### Calendar Date/Time Parsing
+
+`cmd/calendar_time.go` provides flexible date/time parsing: RFC3339, date-only, date+time, time-only, relative (today/tomorrow/+Nd/weekday names). All functions accept `now time.Time` and `loc *time.Location` for testability — never call `time.Now()` directly.
 
 ### Email Encoding
 

README.md

@@ -1,6 +1,6 @@
-# gsuite - Gmail CLI Tool
+# gsuite - Google Workspace CLI Tool
 
-A command-line interface for Gmail mailbox management. Authenticate with your Gmail account via OAuth2 and manage messages, threads, labels, and drafts from the terminal.
+A command-line interface for Google Workspace management. Authenticate with your account via OAuth2 and manage Gmail messages, threads, labels, drafts, and Google Calendar events from the terminal.
 
 ## Installation
 
@@ -22,7 +22,7 @@ go build -o gsuite .
 
 ## Prerequisites
 
-1. **Google Cloud Project** with Gmail API enabled
+1. **Google Cloud Project** with Gmail API and Calendar API enabled
 2. **OAuth2 Client Credentials** (Desktop or Web application type)
 3. Set credentials via environment variable:
    - `GOOGLE_CREDENTIALS` — raw JSON content
@@ -45,6 +45,12 @@ gsuite send --to "user@example.com" --subject "Hello" --body "Message content"
 
 # Search messages
 gsuite search "from:user@example.com is:unread"
+
+# View today's calendar events
+gsuite calendar today
+
+# Create a meeting
+gsuite calendar create --summary "Team Standup" --start "2026-03-15 09:00" --duration 30m
 ```
 
 ## Multi-Account Support
@@ -104,6 +110,15 @@ The `--account` flag (or `GSUITE_ACCOUNT` env var) can be passed to any command
 | `drafts delete <id>` | Delete a draft |
 | `send` | Send an email (supports markdown, attachments) |
 | `search <query>` | Search messages using Gmail query syntax |
+| `calendar list` | List upcoming calendar events |
+| `calendar get <id>` | Get event details including attendees |
+| `calendar create` | Create a calendar event |
+| `calendar update <id>` | Update an existing event |
+| `calendar delete <id>` | Delete a calendar event |
+| `calendar respond <id>` | RSVP to an event invitation |
+| `calendar today` | Show today's events |
+| `calendar week` | Show this week's events (Mon-Sun) |
+| `calendar calendars` | List available calendars |
 | `version` | Show version information |
 | `install-skill` | Install the Claude Code skill for Gmail management |
 
@@ -150,6 +165,20 @@ gsuite labels create -n "My Label"
 # JSON output for scripting
 gsuite messages list -f json
 gsuite search "is:unread" -f json
+
+# Calendar: list upcoming events
+gsuite calendar list --after today --before +7d
+
+# Calendar: create a recurring meeting with attendees
+gsuite calendar create --summary "Weekly 1:1" --start "2026-03-15 10:00" \
+  --duration 30m --rrule "FREQ=WEEKLY;BYDAY=MO" \
+  --attendees "alice@example.com" --send-updates all
+
+# Calendar: RSVP to an event
+gsuite calendar respond abc123def456 --status accepted
+
+# Calendar: delete a recurring event (all instances)
+gsuite calendar delete abc123def456 --recurring-scope all --yes
 ```
 
 ## License