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+# Timezone Implementation Plan
+
+## Overview
+
+Add per-user timezone support with system-wide fallback (set via docker-compose), defaulting to UTC. The database already stores all timestamps as UTC via `TIMESTAMPTZ` columns, so this is primarily a display-layer feature.
+
+**Display format:** MM-DD-YYYY HH:MM (US convention, no timezone abbreviation shown)
+
+**Timezone selection:** Manual dropdown only (no browser auto-detect)
+
+---
+
+## Phase 1: Database Schema
+
+**File:** `database/schema/schema.sql`
+
+1. Add `timezone` column to `users` table:
+
+```sql
+ALTER TABLE users ADD COLUMN IF NOT EXISTS timezone VARCHAR(50) DEFAULT 'UTC';
+```
+
+2. Add system-wide default timezone to `system_settings`:
+
+```sql
+INSERT INTO system_settings (setting_key, setting_value, description) VALUES
+('default_timezone', 'UTC', 'System default timezone')
+ON CONFLICT (setting_key) DO NOTHING;
+```
+
+3. Add index:
+
+```sql
+CREATE INDEX IF NOT EXISTS idx_users_timezone ON users(timezone);
+```
+
+4. Regenerate sqlc code:
+
+```bash
+cd internal/database && sqlc generate
+```
+
+---
+
+## Phase 2: Database Queries
+
+**File:** `internal/database/queries/queries.sql`
+
+Add new queries:
+
+```sql
+-- name: UpdateUserTimezone :exec
+UPDATE users SET timezone = $2, updated_at = NOW() WHERE id = $1;
+
+-- name: GetSystemTimezone :one
+SELECT setting_value FROM system_settings WHERE setting_key = 'default_timezone';
+
+-- name: UpdateSystemTimezone :exec
+UPDATE system_settings SET setting_value = $2, updated_at = NOW() WHERE setting_key = 'default_timezone';
+```
+
+Regenerate after adding queries:
+
+```bash
+cd internal/database && sqlc generate
+```
+
+---
+
+## Phase 3: Template Utilities
+
+**File:** `templates/utils.go`
+
+Add timezone-aware time formatting helpers:
+
+```go
+package templates
+
+import (
+ "time"
+
+ "github.com/jackc/pgx/v5/pgtype"
+)
+
+// FormatInTimezone formats a time.Time in the specified timezone as MM-DD-YYYY HH:MM
+func FormatInTimezone(t time.Time, timezone string) string {
+ if t.IsZero() {
+ return ""
+ }
+
+ loc, err := time.LoadLocation(timezone)
+ if err != nil {
+ loc = time.UTC
+ }
+
+ return t.In(loc).Format("01-02-2006 15:04")
+}
+
+// FormatTimestamptzInTimezone formats a pgtype.Timestamptz in the specified timezone
+func FormatTimestamptzInTimezone(t pgtype.Timestamptz, timezone string) string {
+ if !t.Valid {
+ return ""
+ }
+ return FormatInTimezone(t.Time, timezone)
+}
+```
+
+---
+
+## Phase 4: User Context Update
+
+**File:** `templates/types.go`
+
+Add `Timezone` field to the `User` struct:
+
+```go
+type User struct {
+ ID string
+ Email string
+ Username string
+ Role string
+ Theme string
+ FirstName string
+ LastName string
+ CreatedAt time.Time
+ Token string
+ Timezone string
+}
+```
+
+**File:** `internal/router/helpers.go`
+
+Update `getTemplateUserWithTheme()` to include timezone:
+
+```go
+userTimezone := "UTC"
+if userDB.Timezone.Valid {
+ userTimezone = userDB.Timezone.String
+}
+
+return templates.User{
+ // ... existing fields ...
+ Timezone: userTimezone,
+}
+```
+
+---
+
+## Phase 5: Handlers
+
+**File:** `internal/handlers/auth.go`
+
+Update `UpdateProfileRequest` struct:
+
+```go
+type UpdateProfileRequest struct {
+ Username string `json:"username,omitempty" validate:"omitempty,min=3,max=50"`
+ Email string `json:"email,omitempty" validate:"omitempty,email"`
+ FirstName string `json:"first_name,omitempty" validate:"omitempty,max=100"`
+ LastName string `json:"last_name,omitempty" validate:"omitempty,max=100"`
+ Theme string `json:"theme,omitempty" validate:"omitempty"`
+ Timezone string `json:"timezone,omitempty" validate:"omitempty"`
+}
+```
+
+Add timezone update logic in `UpdateProfile()`:
+
+```go
+if req.Timezone != "" {
+ if _, err := time.LoadLocation(req.Timezone); err != nil {
+ return c.JSON(http.StatusBadRequest, map[string]string{
+ "error": "Invalid timezone",
+ })
+ }
+ err := h.db.UpdateUserTimezone(ctx, database.UpdateUserTimezoneParams{
+ ID: pgtype.UUID{Bytes: userUUID, Valid: true},
+ Timezone: pgtype.Text{String: req.Timezone, Valid: true},
+ })
+ if err != nil {
+ return err
+ }
+}
+```
+
+**File:** `internal/handlers/system_settings.go`
+
+Add timezone settings handler:
+
+```go
+type UpdateTimezoneSettingsRequest struct {
+ DefaultTimezone string `json:"default_timezone" validate:"required"`
+}
+
+func (h *SystemSettingsHandler) UpdateTimezoneSettings(c *echo.Context) error {
+ var req UpdateTimezoneSettingsRequest
+ if err := c.Bind(&req); err != nil {
+ return c.JSON(http.StatusBadRequest, map[string]string{"error": "Invalid request"})
+ }
+ if _, err := time.LoadLocation(req.DefaultTimezone); err != nil {
+ return c.JSON(http.StatusBadRequest, map[string]string{"error": "Invalid timezone"})
+ }
+ err := h.db.UpdateSystemTimezone(c.Request().Context(), database.UpdateSystemTimezoneParams{
+ SettingKey: "default_timezone",
+ SettingValue: req.DefaultTimezone,
+ })
+ if err != nil {
+ return err
+ }
+ return c.JSON(http.StatusOK, map[string]string{"message": "Timezone updated"})
+}
+```
+
+---
+
+## Phase 6: User Profile UI
+
+**File:** `templates/profile_form.templ`
+
+Add timezone dropdown after the theme field:
+
+```templ
+
+
+
+
+```
+
+Include timezone in the HTMX form submission payload.
+
+---
+
+## Phase 7: Admin Settings UI
+
+**File:** `templates/admin_settings.templ`
+
+Add system default timezone setting:
+
+```templ
+
+
System Defaults
+
+
+
+```
+
+---
+
+## Phase 8: Template Time Display Updates
+
+### Files to update
+
+| Template | Line(s) | Field(s) |
+|----------|---------|----------|
+| `templates/book_detail.templ` | ~253, ~282 | `LastReadAt`, `DatePublished` |
+| `templates/book_detail_modals.templ` | ~68, ~113 | `Timestamp`, `LastReadAt` |
+| `templates/devices.templ` | ~83, ~91, ~174 | `LastSync`, `LastSeen`, `ExpiresAt` |
+| `templates/conflicts.templ` | ~114 | `CreatedAt` |
+| `templates/admin_users.templ` | ~89 | `CreatedAt` |
+| `templates/queue.templ` | ~138 | `CreatedAt` |
+
+### Change pattern
+
+```templ
+
+{ book.ReadingProgress.LastReadAt.Time.Format("2006-01-02 15:04") }
+
+
+{ templates.FormatTimestamptzInTimezone(book.ReadingProgress.LastReadAt, user.Timezone) }
+```
+
+For `time.Time` fields:
+
+```templ
+
+{ device.LastSync.Format("2006-01-02 15:04") }
+
+
+{ templates.FormatInTimezone(device.LastSync, user.Timezone) }
+```
+
+---
+
+## Phase 9: Docker Configuration
+
+**File:** `docker-compose.yml`
+
+```yaml
+services:
+ server:
+ environment:
+ - TZ=UTC
+```
+
+**File:** `.env.example`
+
+```
+# System default timezone (fallback if not set in DB)
+TZ=UTC
+```
+
+---
+
+## Files Modified Summary
+
+| File | Change |
+|------|--------|
+| `database/schema/schema.sql` | Add timezone column to users, system_setting row |
+| `internal/database/queries/queries.sql` | Add UpdateUserTimezone, GetSystemTimezone, UpdateSystemTimezone |
+| `templates/utils.go` | Add FormatInTimezone, FormatTimestamptzInTimezone |
+| `templates/types.go` | Add Timezone field to User struct |
+| `internal/router/helpers.go` | Pass timezone to template User |
+| `internal/handlers/auth.go` | Handle timezone updates in UpdateProfile |
+| `internal/handlers/system_settings.go` | Add timezone settings handler |
+| `templates/profile_form.templ` | Add timezone dropdown |
+| `templates/admin_settings.templ` | Add default timezone setting |
+| `templates/book_detail.templ` | Update time displays |
+| `templates/book_detail_modals.templ` | Update time displays |
+| `templates/devices.templ` | Update time displays |
+| `templates/conflicts.templ` | Update time displays |
+| `templates/admin_users.templ` | Update time displays |
+| `templates/queue.templ` | Update time displays |
+| `docker-compose.yml` | Add TZ env var |
+| `.env.example` | Add TZ example |
+
+---
+
+## Testing Checklist
+
+- [ ] Create user, set timezone to Eastern, verify times display in MM-DD-YYYY HH:MM format
+- [ ] Create user, set timezone to Pacific, verify different offset
+- [ ] Test system default timezone fallback for users with no timezone set
+- [ ] Verify invalid timezone values are rejected by the API
+- [ ] Verify existing users (no timezone set) fall back to system default
+- [ ] Verify all templates show consistent MM-DD-YYYY HH:MM format
+- [ ] Run `make test-integration` to verify no regressions
+
+---
+
+## Deployment Steps
+
+1. Update `database/schema/schema.sql` with new column and settings
+2. Regenerate sqlc: `cd internal/database && sqlc generate`
+3. Apply schema changes (restart database container with `make rebuild-force-db`)
+4. Deploy backend code changes
+5. Verify with existing data