diff --git a/caldav/caldav.go b/caldav/caldav.go
new file mode 100644
index 0000000..29b45b7
--- /dev/null
+++ b/caldav/caldav.go
@@ -0,0 +1,272 @@
+package caldav
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"path"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/ProtonMail/go-crypto/openpgp"
+	"github.com/emersion/go-ical"
+	"github.com/emersion/go-webdav"
+	"github.com/emersion/go-webdav/caldav"
+	"github.com/emersion/hydroxide/protonmail"
+)
+
+var errNotFound = errors.New("caldav: not found")
+
+type backend struct {
+	c           *protonmail.Client
+	cache       map[string]*protonmail.Calendar
+	eventCache  map[string]map[string]*protonmail.CalendarEvent // calendarID -> eventID -> event
+	locker      sync.Mutex
+	privateKeys openpgp.EntityList
+}
+
+func (b *backend) CurrentUserPrincipal(ctx context.Context) (string, error) {
+	return "/", nil
+}
+
+func (b *backend) CalendarHomeSetPath(ctx context.Context) (string, error) {
+	return "/calendars", nil
+}
+
+func (b *backend) CreateCalendar(ctx context.Context, cal *caldav.Calendar) error {
+	return webdav.NewHTTPError(http.StatusForbidden, errors.New("cannot create new calendar"))
+}
+
+func (b *backend) DeleteCalendar(ctx context.Context, path string) error {
+	return webdav.NewHTTPError(http.StatusForbidden, errors.New("cannot delete calendar"))
+}
+
+func (b *backend) ListCalendars(ctx context.Context) ([]caldav.Calendar, error) {
+	b.locker.Lock()
+	defer b.locker.Unlock()
+
+	if b.cache == nil {
+		calendars, err := b.c.ListCalendars(0, 0)
+		if err != nil {
+			return nil, err
+		}
+		b.cache = make(map[string]*protonmail.Calendar)
+		for _, cal := range calendars {
+			b.cache[cal.ID] = cal
+		}
+	}
+
+	var result []caldav.Calendar
+	for _, cal := range b.cache {
+		result = append(result, caldav.Calendar{
+			Path:            "/calendars/" + cal.ID + "/",
+			Name:            cal.Name,
+			Description:     cal.Description,
+			MaxResourceSize: 10 * 1024 * 1024, // 10MB
+		})
+	}
+
+	return result, nil
+}
+
+func (b *backend) GetCalendar(ctx context.Context, path string) (*caldav.Calendar, error) {
+	calID, err := parseCalendarPath(path)
+	if err != nil {
+		return nil, err
+	}
+
+	calendars, err := b.ListCalendars(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, cal := range calendars {
+		if strings.TrimSuffix(cal.Path, "/") == "/calendars/"+calID {
+			return &cal, nil
+		}
+	}
+
+	return nil, webdav.NewHTTPError(http.StatusNotFound, errors.New("calendar not found"))
+}
+
+func parseCalendarPath(p string) (string, error) {
+	parts := strings.Split(strings.Trim(p, "/"), "/")
+	if len(parts) < 2 || parts[0] != "calendars" {
+		return "", errNotFound
+	}
+	return parts[1], nil
+}
+
+func parseObjectPath(p string) (calendarID, eventID string, err error) {
+	parts := strings.Split(strings.Trim(p, "/"), "/")
+	if len(parts) != 3 || parts[0] != "calendars" {
+		return "", "", errNotFound
+	}
+	ext := path.Ext(parts[2])
+	if ext != ".ics" {
+		return "", "", errNotFound
+	}
+	return parts[1], strings.TrimSuffix(parts[2], ext), nil
+}
+
+func formatObjectPath(calendarID, eventID string) string {
+	return "/calendars/" + calendarID + "/" + eventID + ".ics"
+}
+
+func (b *backend) toCalendarObject(event *protonmail.CalendarEvent, cal *protonmail.Calendar) (*caldav.CalendarObject, error) {
+	// Create a basic iCal event
+	calObj := &caldav.CalendarObject{
+		Path:    formatObjectPath(cal.ID, event.ID),
+		ModTime: time.Unix(event.CreateTime.Unix(), 0),
+		ETag:    fmt.Sprintf("%x", event.LastEditTime),
+	}
+
+	// Parse the event data from CalendarEventCard
+	for _, card := range event.PersonalEvent {
+		if card.Data != "" {
+			decoded, err := ical.NewDecoder(strings.NewReader(card.Data)).Decode()
+			if err != nil {
+				continue
+			}
+			calObj.Data = decoded
+			break
+		}
+	}
+
+	if calObj.Data == nil {
+		// Create a basic calendar if no data
+		calObj.Data = ical.NewCalendar()
+	}
+
+	return calObj, nil
+}
+
+func (b *backend) GetCalendarObject(ctx context.Context, path string, req *caldav.CalendarCompRequest) (*caldav.CalendarObject, error) {
+	calID, eventID, err := parseObjectPath(path)
+	if err != nil {
+		return nil, err
+	}
+
+	// Get calendar
+	cal, ok := b.cache[calID]
+	if !ok {
+		calendars, err := b.c.ListCalendars(0, 0)
+		if err != nil {
+			return nil, err
+		}
+		for _, c := range calendars {
+			if c.ID == calID {
+				cal = c
+				break
+			}
+		}
+		if cal == nil {
+			return nil, errNotFound
+		}
+	}
+
+	// Get event
+	filter := &protonmail.CalendarEventFilter{
+		Start:    time.Now().AddDate(-1, 0, 0).Unix(),
+		End:      time.Now().AddDate(1, 0, 0).Unix(),
+		Timezone: "UTC",
+		Page:     0,
+	}
+
+	events, err := b.c.ListCalendarEvents(calID, filter)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, event := range events {
+		if event.ID == eventID {
+			return b.toCalendarObject(event, cal)
+		}
+	}
+
+	return nil, errNotFound
+}
+
+func (b *backend) ListCalendarObjects(ctx context.Context, path string, req *caldav.CalendarCompRequest) ([]caldav.CalendarObject, error) {
+	calID, err := parseCalendarPath(path)
+	if err != nil {
+		return nil, err
+	}
+
+	// Get calendar
+	cal, ok := b.cache[calID]
+	if !ok {
+		calendars, err := b.c.ListCalendars(0, 0)
+		if err != nil {
+			return nil, err
+		}
+		for _, c := range calendars {
+			if c.ID == calID {
+				cal = c
+				break
+			}
+		}
+		if cal == nil {
+			return nil, errNotFound
+		}
+	}
+
+	// Get events
+	filter := &protonmail.CalendarEventFilter{
+		Start:    time.Now().AddDate(-1, 0, 0).Unix(),
+		End:      time.Now().AddDate(1, 0, 0).Unix(),
+		Timezone: "UTC",
+		Page:     0,
+	}
+
+	events, err := b.c.ListCalendarEvents(calID, filter)
+	if err != nil {
+		return nil, err
+	}
+
+	var result []caldav.CalendarObject
+	for _, event := range events {
+		obj, err := b.toCalendarObject(event, cal)
+		if err != nil {
+			continue
+		}
+		result = append(result, *obj)
+	}
+
+	return result, nil
+}
+
+func (b *backend) QueryCalendarObjects(ctx context.Context, path string, query *caldav.CalendarQuery) ([]caldav.CalendarObject, error) {
+	req := caldav.CalendarCompRequest{AllProps: true}
+	if query != nil {
+		req = query.CompRequest
+	}
+	return b.ListCalendarObjects(ctx, path, &req)
+}
+
+func (b *backend) PutCalendarObject(ctx context.Context, path string, cal *ical.Calendar, opts *caldav.PutCalendarObjectOptions) (*caldav.CalendarObject, error) {
+	// TODO: Implement creating/updating calendar events
+	return nil, webdav.NewHTTPError(http.StatusNotImplemented, errors.New("calendar event creation not yet implemented"))
+}
+
+func (b *backend) DeleteCalendarObject(ctx context.Context, path string) error {
+	// TODO: Implement deleting calendar events
+	return webdav.NewHTTPError(http.StatusNotImplemented, errors.New("calendar event deletion not yet implemented"))
+}
+
+func NewHandler(c *protonmail.Client, privateKeys openpgp.EntityList, events <-chan *protonmail.Event) http.Handler {
+	if len(privateKeys) == 0 {
+		panic("hydroxide/caldav: no private key available")
+	}
+
+	b := &backend{
+		c:           c,
+		cache:       make(map[string]*protonmail.Calendar),
+		eventCache:  make(map[string]map[string]*protonmail.CalendarEvent),
+		privateKeys: privateKeys,
+	}
+
+	return &caldav.Handler{Backend: b}
+}
\ No newline at end of file
diff --git a/go.mod b/go.mod
index fd8a229..c7d6217 100644
--- a/go.mod
+++ b/go.mod
@@ -1,10 +1,11 @@
 module github.com/emersion/hydroxide
 
-go 1.24.0
+go 1.22
 
 require (
 	github.com/ProtonMail/go-crypto v1.3.0
 	github.com/emersion/go-bcrypt v0.0.0-20170822072041-6e724a1baa63
+	github.com/emersion/go-ical v0.0.0-20240127095438-fc1c9d8fb2b6
 	github.com/emersion/go-imap v1.2.1
 	github.com/emersion/go-mbox v1.0.4
 	github.com/emersion/go-message v0.18.2
diff --git a/go.sum b/go.sum
index 1f2adb9..49f9667 100644
--- a/go.sum
+++ b/go.sum
@@ -6,6 +6,7 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/emersion/go-bcrypt v0.0.0-20170822072041-6e724a1baa63 h1:7aCSuwTBzg7BCPRRaBJD0weKZYdeAykOrY6ktpx8Vvc=
 github.com/emersion/go-bcrypt v0.0.0-20170822072041-6e724a1baa63/go.mod h1:eRwwJnuLVFtYTC+AI2JDJTMcuQUTYhBIK4I6bC5tpqw=
+github.com/emersion/go-ical v0.0.0-20240127095438-fc1c9d8fb2b6 h1:F6kGPGTlORycwgD7gsKlB81RJ4e0Ey//t8PQ5/vQjlE=
 github.com/emersion/go-ical v0.0.0-20240127095438-fc1c9d8fb2b6/go.mod h1:BEksegNspIkjCQfmzWgsgbu6KdeJ/4LwUZs7DMBzjzw=
 github.com/emersion/go-imap v1.2.1 h1:+s9ZjMEjOB8NzZMVTM3cCenz2JrQIGGo5j1df19WjTA=
 github.com/emersion/go-imap v1.2.1/go.mod h1:Qlx1FSx2FTxjnjWpIlVNEuX+ylerZQNFE5NsmKFSejY=