diff --git a/src/app/calendar.ts b/src/app/calendar.ts
index 979a720d..eee59e5c 100644
--- a/src/app/calendar.ts
+++ b/src/app/calendar.ts
@@ -6,15 +6,17 @@ import {
   pushToMapKey,
   secondsToDate,
   sortBy,
+  spec,
   uniqBy,
 } from "@welshman/lib"
-import {EVENT_RSVP, getAddress, makeEvent, tagSpec, tagValue} from "@welshman/util"
+import {EVENT_RSVP, getAddress, tagSpec, tagValue} from "@welshman/util"
 import type {TrustedEvent} from "@welshman/util"
-import {TimeEvent} from "@welshman/domain"
+import {CalendarRsvp, TimeEvent} from "@welshman/domain"
+import type {RsvpStatus} from "@welshman/domain"
 import {synced} from "@welshman/store"
-import {deletes, reader, relays, thunks} from "@app/core"
+import {deletes, reader, relays, thunks, writer} from "@app/core"
 import {deriveEvents} from "@app/repository"
-import {PROTECTED} from "@app/rooms"
+import {toSpace} from "@app/rooms"
 import {kv} from "@app/storage"
 
 // Views
@@ -230,12 +232,6 @@ export const layoutMultiDayBars = (
 
 // RSVPs (NIP-52)
 
-export enum RsvpStatus {
-  Accepted = "accepted",
-  Declined = "declined",
-  Tentative = "tentative",
-}
-
 export const makeRsvpFilter = (event: TrustedEvent) => ({
   kinds: [EVENT_RSVP],
   "#a": [getAddress(event)],
@@ -243,10 +239,7 @@ export const makeRsvpFilter = (event: TrustedEvent) => ({
 
 export const deriveRsvps = (event: TrustedEvent) => deriveEvents([makeRsvpFilter(event)])
 
-export const getRsvpStatus = (rsvp: TrustedEvent) => tagValue(tagSpec("status"), rsvp.tags)
-
-export const isAttending = (status?: string) =>
-  status === RsvpStatus.Accepted || status === RsvpStatus.Tentative
+export const isAttending = (status?: RsvpStatus) => status === "accepted" || status === "tentative"
 
 // A relay can still hold a replaced RSVP, so the newest per person is the one that counts.
 export const getRsvpsByStatus = (rsvps: TrustedEvent[]) => {
@@ -256,37 +249,32 @@ export const getRsvpsByStatus = (rsvps: TrustedEvent[]) => {
   )
 
   const byStatus = (status: RsvpStatus) =>
-    latest.filter(rsvp => getRsvpStatus(rsvp) === status).map(rsvp => rsvp.pubkey)
+    latest.filter(rsvp => reader(CalendarRsvp)(rsvp).status() === status).map(rsvp => rsvp.pubkey)
 
   return {
     latest,
-    accepted: byStatus(RsvpStatus.Accepted),
-    tentative: byStatus(RsvpStatus.Tentative),
-    declined: byStatus(RsvpStatus.Declined),
+    accepted: byStatus("accepted"),
+    tentative: byStatus("tentative"),
+    declined: byStatus("declined"),
   }
 }
 
 // An RSVP is addressable, so identifying it by its target makes a new one supersede the old.
 export const publishRsvp = async (url: string, event: TrustedEvent, status: RsvpStatus) => {
-  const address = getAddress(event)
-  const h = tagValue(tagSpec("h"), event.tags)
-  const tags = [
-    ["a", address, url],
-    ["e", event.id, url],
-    ["d", address],
-    ["status", status],
-    ["p", event.pubkey],
-  ]
+  const eventWriter = await toSpace(
+    writer(CalendarRsvp)
+      .setIdentifier(getAddress(event))
+      .setCalendarEventFromEvent(event)
+      .setStatus(status)
+      // The writer hints the organizer's outbox, but a space's event lives on the space relay.
+      .dropTags(spec(["a"]))
+      .dropTags(spec(["e"]))
+      .addTags(["a", getAddress(event), url], ["e", event.id, url]),
+    url,
+    reader(TimeEvent)(event).room(),
+  )
 
-  if (await relays.get().hasNip(url, 70)) {
-    tags.push(PROTECTED)
-  }
-
-  if (h) {
-    tags.push(["h", h])
-  }
-
-  return thunks.get().publish({relays: [url], event: makeEvent(EVENT_RSVP, {tags})})
+  return thunks.get().publish({relays: [url], event: await eventWriter.renderTemplate()})
 }
 
 export const retractRsvp = async (url: string, rsvp: TrustedEvent) => {
diff --git a/src/app/components/CalendarRsvp.svelte b/src/app/components/CalendarRsvp.svelte
index fed35ecc..f4a4ce4d 100644
--- a/src/app/components/CalendarRsvp.svelte
+++ b/src/app/components/CalendarRsvp.svelte
@@ -1,6 +1,8 @@
 <script lang="ts">
   import cx from "classnames"
   import type {TrustedEvent} from "@welshman/util"
+  import {CalendarRsvp} from "@welshman/domain"
+  import type {RsvpStatus} from "@welshman/domain"
   import CheckCircle from "@assets/icons/check-circle.svg?dataurl"
   import QuestionCircle from "@assets/icons/question-circle.svg?dataurl"
   import CloseCircle from "@assets/icons/close-circle.svg?dataurl"
@@ -8,15 +10,8 @@
   import Button from "@lib/components/Button.svelte"
   import Spinner from "@lib/components/Spinner.svelte"
   import ProfileCircles from "@app/components/ProfileCircles.svelte"
-  import {user} from "@app/core"
-  import {
-    RsvpStatus,
-    getRsvpStatus,
-    getRsvpsByStatus,
-    isAttending,
-    publishRsvp,
-    retractRsvp,
-  } from "@app/calendar"
+  import {reader, user} from "@app/core"
+  import {getRsvpsByStatus, isAttending, publishRsvp, retractRsvp} from "@app/calendar"
   import {setEventReminders} from "@app/reminders"
 
   type Props = {
@@ -35,7 +30,7 @@
 
     loading = true
 
-    const retracting = ownRsvp && getRsvpStatus(ownRsvp) === status
+    const retracting = ownRsvp && ownStatus === status
 
     try {
       if (retracting) {
@@ -50,11 +45,11 @@
     }
   }
 
-  const accept = () => setStatus(RsvpStatus.Accepted)
+  const accept = () => setStatus("accepted")
 
-  const maybe = () => setStatus(RsvpStatus.Tentative)
+  const maybe = () => setStatus("tentative")
 
-  const decline = () => setStatus(RsvpStatus.Declined)
+  const decline = () => setStatus("declined")
 
   const statusClass = (status: RsvpStatus) =>
     cx("button button-xs join-item", ownStatus === status ? "button-primary" : "button-neutral")
@@ -63,7 +58,7 @@
 
   const people = $derived(getRsvpsByStatus(rsvps))
   const ownRsvp = $derived(people.latest.find(rsvp => rsvp.pubkey === $user.pubkey))
-  const ownStatus = $derived(ownRsvp ? getRsvpStatus(ownRsvp) : undefined)
+  const ownStatus = $derived(ownRsvp ? reader(CalendarRsvp)(ownRsvp).status() : undefined)
   const attending = $derived([...people.accepted, ...people.tentative])
 </script>
 
@@ -71,15 +66,15 @@
   <div class="flex flex-wrap items-center gap-2">
     <span class="text-sm opacity-75">Are you going?</span>
     <div class="join">
-      <Button class={statusClass(RsvpStatus.Accepted)} disabled={loading} onclick={accept}>
+      <Button class={statusClass("accepted")} disabled={loading} onclick={accept}>
         <Icon icon={CheckCircle} size={4} />
         Going
       </Button>
-      <Button class={statusClass(RsvpStatus.Tentative)} disabled={loading} onclick={maybe}>
+      <Button class={statusClass("tentative")} disabled={loading} onclick={maybe}>
         <Icon icon={QuestionCircle} size={4} />
         Maybe
       </Button>
-      <Button class={statusClass(RsvpStatus.Declined)} disabled={loading} onclick={decline}>
+      <Button class={statusClass("declined")} disabled={loading} onclick={decline}>
         <Icon icon={CloseCircle} size={4} />
         Can't go
       </Button>
diff --git a/src/app/feeds.ts b/src/app/feeds.ts
index eeb09e07..87d070ac 100644
--- a/src/app/feeds.ts
+++ b/src/app/feeds.ts
@@ -15,10 +15,9 @@ import {
   hexTags,
   isReplaceableKind,
   matchFilters,
-  tagSpec,
-  tagValue,
   tagValues,
 } from "@welshman/util"
+import {TimeEvent} from "@welshman/domain"
 import type {Maybe} from "@welshman/lib"
 import type {Filter, TrustedEvent} from "@welshman/util"
 import {mergeRepositoryUpdates} from "@welshman/net"
@@ -27,7 +26,7 @@ import {createScroller} from "@lib/html"
 import type {ScrollerOpts} from "@lib/html"
 import {daysBetween} from "@lib/util"
 import {EVENT_CONTEXT_KINDS, REACTION_KINDS} from "@app/content"
-import {app, network} from "@app/core"
+import {app, network, reader} from "@app/core"
 import {getEventsForUrl} from "@app/repository"
 
 const noEvents: TrustedEvent[] = []
@@ -682,13 +681,17 @@ export const makeCalendarFeed = ({
   let oldest = now()
   let newest = now()
 
-  const getStart = (event: TrustedEvent) => parseInt(tagValue(tagSpec("start"), event.tags) || "")
-
-  const getEnd = (event: TrustedEvent) => parseInt(tagValue(tagSpec("end"), event.tags) || "")
+  const getStart = (event: TrustedEvent) => reader(TimeEvent)(event).start() ?? 0
 
   const compareByStart = (a: TrustedEvent, b: TrustedEvent) =>
     getStart(a) - getStart(b) || compareEventsAsc(a, b)
 
+  const isValid = (event: TrustedEvent) => {
+    const timeEvent = reader(TimeEvent)(event)
+
+    return timeEvent.start() && timeEvent.end() && !seen.has(event.id)
+  }
+
   const events = writable(
     uniqBy(
       e => e.id,
@@ -697,7 +700,7 @@ export const makeCalendarFeed = ({
   )
 
   const insertEvents = (newEvents: TrustedEvent[]) => {
-    const valid = newEvents.filter(e => !isNaN(getStart(e)) && !isNaN(getEnd(e)) && !seen.has(e.id))
+    const valid = newEvents.filter(isValid)
 
     if (valid.length === 0) {
       return
diff --git a/src/app/reminders.ts b/src/app/reminders.ts
index 4d67f1ed..2e5397ed 100644
--- a/src/app/reminders.ts
+++ b/src/app/reminders.ts
@@ -1,9 +1,10 @@
-import {MINUTE, formatTimestampRelative, int, ms, now, uniq} from "@welshman/lib"
-import {EVENT_RSVP, addressTags, getIdFilters, isSignedEvent, matchTag} from "@welshman/util"
+import {MINUTE, first, formatTimestampRelative, int, ms, now, uniq} from "@welshman/lib"
+import {EVENT_RSVP, getIdFilters, isSignedEvent} from "@welshman/util"
 import type {TrustedEvent} from "@welshman/util"
+import {CalendarRsvp} from "@welshman/domain"
 import {buildUrl} from "@lib/util"
-import {getEventStart, getEventTitle, getRsvpStatus, isAttending} from "@app/calendar"
-import {app, network, roomLists} from "@app/core"
+import {getEventStart, getEventTitle, isAttending} from "@app/calendar"
+import {app, network, reader, roomLists} from "@app/core"
 import {PUSH_SERVER} from "@app/env"
 import {pushState} from "@app/push/adapters/common"
 import {notificationSettings} from "@app/settings"
@@ -70,14 +71,16 @@ const loadAttendedEvents = async (pubkey: string) => {
 
   await $network.request({signal, filters, relays, autoClose: true})
 
-  const attended = app
-    .get()
-    .repository.query(filters)
-    .flatMap(rsvp => {
-      const tag = matchTag(addressTags("a"), rsvp.tags)
+  const {repository, tracker} = app.get()
 
-      return tag?.[2] && isAttending(getRsvpStatus(rsvp)) ? [{address: tag[1], relay: tag[2]}] : []
-    })
+  // An RSVP only goes to the space holding its event, so where it was seen is where the event is.
+  const attended = repository.query(filters).flatMap(rsvp => {
+    const rsvpReader = reader(CalendarRsvp)(rsvp)
+    const address = rsvpReader.calendarEvent()
+    const relay = first(Array.from(tracker.getRelays(rsvp.id)))
+
+    return address && relay && isAttending(rsvpReader.status()) ? [{address, relay}] : []
+  })
 
   await $network.request({
     signal,
diff --git a/src/app/title.ts b/src/app/title.ts
index 84500fba..df213df8 100644
--- a/src/app/title.ts
+++ b/src/app/title.ts
@@ -3,6 +3,7 @@ import {tagSpec, tagValue} from "@welshman/util"
 import {displayPubkey} from "@welshman/domain"
 import {makeRoomKey} from "@welshman/app"
 import {decodePubkey} from "@lib/util"
+import {getEventTitle} from "@app/calendar"
 import {app, profiles, rooms} from "@app/core"
 import {PLATFORM_NAME} from "@app/env"
 import {decodeRelay} from "@app/relays"
@@ -137,7 +138,7 @@ export const getPageTitle = ({page, pubkey}: PageTitleContext) => {
   }
 
   if (routeId === "/spaces/[relay]/calendar/[address]") {
-    return makeTitle(tagValue(tagSpec("title"), event?.tags || []) || "Event")
+    return makeTitle((event && getEventTitle(event)) || "Event")
   }
 
   if (routeId === "/spaces/[relay]/classifieds/[address]") {