diff --git a/keyserver/src/endpoints.js b/keyserver/src/endpoints.js
--- a/keyserver/src/endpoints.js
+++ b/keyserver/src/endpoints.js
@@ -6,6 +6,7 @@
 import { baseLegalPolicies } from 'lib/facts/policies.js';
 import type { PolicyType } from 'lib/facts/policies.js';
 import type { Endpoint } from 'lib/types/endpoints.js';
+import { calendarQueryValidator } from 'lib/types/entry-types.js';
 import { endpointValidators } from 'lib/types/validators/endpoint-validators.js';
 import { updateUserAvatarRequestValidator } from 'lib/utils/avatar-utils.js';
 
@@ -32,7 +33,6 @@
   deleteEntryRequestInputValidator,
   entryQueryInputValidator,
   entryRevisionHistoryFetchInputValidator,
-  newEntryQueryInputValidator,
   restoreEntryRequestInputValidator,
   saveEntryRequestInputValidator,
 } from './responders/entry-responders.js';
@@ -396,7 +396,7 @@
   },
   update_calendar_query: {
     responder: calendarQueryUpdateResponder,
-    inputValidator: newEntryQueryInputValidator,
+    inputValidator: calendarQueryValidator,
     policies: baseLegalPolicies,
   },
   update_user_settings: {
diff --git a/keyserver/src/responders/entry-responders.js b/keyserver/src/responders/entry-responders.js
--- a/keyserver/src/responders/entry-responders.js
+++ b/keyserver/src/responders/entry-responders.js
@@ -15,17 +15,19 @@
   type FetchEntryInfosResponse,
   type DeltaEntryInfosResult,
   type SaveEntryResponse,
+  calendarQueryValidator,
 } from 'lib/types/entry-types.js';
 import {
   type CalendarFilter,
   calendarThreadFilterTypes,
+  calendarFilterValidator,
 } from 'lib/types/filter-types.js';
 import {
   type FetchEntryRevisionInfosResult,
   type FetchEntryRevisionInfosRequest,
 } from 'lib/types/history-types.js';
 import { ServerError } from 'lib/utils/errors.js';
-import { tString, tShape, tDate, tID } from 'lib/utils/validation-utils.js';
+import { tShape, tDate, tID } from 'lib/utils/validation-utils.js';
 
 import createEntry from '../creators/entry-creator.js';
 import { deleteEntry, restoreEntry } from '../deleters/entry-deleters.js';
@@ -55,37 +57,9 @@
     startDate: tDate,
     endDate: tDate,
     includeDeleted: t.maybe(t.Boolean),
-    filters: t.maybe(
-      t.list(
-        t.union([
-          tShape({
-            type: tString(calendarThreadFilterTypes.NOT_DELETED),
-          }),
-          tShape({
-            type: tString(calendarThreadFilterTypes.THREAD_LIST),
-            threadIDs: t.list(tID),
-          }),
-        ]),
-      ),
-    ),
+    filters: t.maybe(t.list(calendarFilterValidator)),
   });
 
-const newEntryQueryInputValidator: TInterface<CalendarQuery> = tShape({
-  startDate: tDate,
-  endDate: tDate,
-  filters: t.list(
-    t.union([
-      tShape({
-        type: tString(calendarThreadFilterTypes.NOT_DELETED),
-      }),
-      tShape({
-        type: tString(calendarThreadFilterTypes.THREAD_LIST),
-        threadIDs: t.list(tID),
-      }),
-    ]),
-  ),
-});
-
 function normalizeCalendarQuery(input: any): CalendarQuery {
   if (input.filters) {
     return {
@@ -159,7 +133,7 @@
     date: tDate,
     threadID: tID,
     localID: t.maybe(t.String),
-    calendarQuery: t.maybe(newEntryQueryInputValidator),
+    calendarQuery: t.maybe(calendarQueryValidator),
   });
 
 async function entryCreationResponder(
@@ -176,7 +150,7 @@
     prevText: t.String,
     sessionID: t.maybe(t.String),
     timestamp: t.Number,
-    calendarQuery: t.maybe(newEntryQueryInputValidator),
+    calendarQuery: t.maybe(calendarQueryValidator),
   });
 
 async function entryUpdateResponder(
@@ -192,7 +166,7 @@
     prevText: t.String,
     sessionID: t.maybe(t.String),
     timestamp: t.Number,
-    calendarQuery: t.maybe(newEntryQueryInputValidator),
+    calendarQuery: t.maybe(calendarQueryValidator),
   });
 
 async function entryDeletionResponder(
@@ -207,7 +181,7 @@
     entryID: tID,
     sessionID: t.maybe(t.String),
     timestamp: t.Number,
-    calendarQuery: t.maybe(newEntryQueryInputValidator),
+    calendarQuery: t.maybe(calendarQueryValidator),
   });
 
 async function entryRestorationResponder(
@@ -244,7 +218,6 @@
 
 export {
   entryQueryInputValidator,
-  newEntryQueryInputValidator,
   normalizeCalendarQuery,
   verifyCalendarQueryThreadIDs,
   entryFetchResponder,
diff --git a/keyserver/src/responders/report-responders.js b/keyserver/src/responders/report-responders.js
--- a/keyserver/src/responders/report-responders.js
+++ b/keyserver/src/responders/report-responders.js
@@ -4,6 +4,7 @@
 import t from 'tcomb';
 import type { TInterface, TStructProps, TUnion } from 'tcomb';
 
+import { calendarQueryValidator } from 'lib/types/entry-types.js';
 import type { BaseAction } from 'lib/types/redux-types.js';
 import {
   type ReportCreationResponse,
@@ -22,7 +23,6 @@
 import { ServerError } from 'lib/utils/errors.js';
 import { tShape, tPlatformDetails } from 'lib/utils/validation-utils.js';
 
-import { newEntryQueryInputValidator } from './entry-responders.js';
 import createReport from '../creators/report-creator.js';
 import {
   fetchErrorReportInfos,
@@ -55,7 +55,7 @@
     platformDetails: tPlatformDetails,
     beforeAction: t.Object,
     action: t.Object,
-    calendarQuery: newEntryQueryInputValidator,
+    calendarQuery: calendarQueryValidator,
     pollResult: t.maybe(t.Object),
     pushResult: t.Object,
     lastActionTypes: t.maybe(t.list(tActionType)),
diff --git a/keyserver/src/responders/user-responders.js b/keyserver/src/responders/user-responders.js
--- a/keyserver/src/responders/user-responders.js
+++ b/keyserver/src/responders/user-responders.js
@@ -51,6 +51,7 @@
 import {
   type CalendarQuery,
   type FetchEntryInfosBase,
+  calendarQueryValidator,
 } from 'lib/types/entry-types.js';
 import { defaultNumberPerThread } from 'lib/types/message-types.js';
 import type {
@@ -89,7 +90,6 @@
 
 import {
   entryQueryInputValidator,
-  newEntryQueryInputValidator,
   normalizeCalendarQuery,
   verifyCalendarQueryThreadIDs,
 } from './entry-responders.js';
@@ -229,7 +229,7 @@
     username: t.String,
     email: t.maybe(tEmail),
     password: tPassword,
-    calendarQuery: t.maybe(newEntryQueryInputValidator),
+    calendarQuery: t.maybe(calendarQueryValidator),
     deviceTokenUpdateRequest: t.maybe(deviceTokenUpdateRequestInputValidator),
     platformDetails: tPlatformDetails,
     // We include `primaryIdentityPublicKey` to avoid breaking
diff --git a/keyserver/src/socket/socket.js b/keyserver/src/socket/socket.js
--- a/keyserver/src/socket/socket.js
+++ b/keyserver/src/socket/socket.js
@@ -17,7 +17,10 @@
 import { mostRecentUpdateTimestamp } from 'lib/shared/update-utils.js';
 import { hasMinCodeVersion } from 'lib/shared/version-utils.js';
 import { endpointIsSocketSafe } from 'lib/types/endpoints.js';
-import type { RawEntryInfo } from 'lib/types/entry-types.js';
+import {
+  type RawEntryInfo,
+  calendarQueryValidator,
+} from 'lib/types/entry-types.js';
 import { defaultNumberPerThread } from 'lib/types/message-types.js';
 import { redisMessageTypes, type RedisMessage } from 'lib/types/redis-types.js';
 import { serverRequestTypes } from 'lib/types/request-types.js';
@@ -67,10 +70,7 @@
   getMessageFetchResultFromRedisMessages,
 } from '../fetchers/message-fetchers.js';
 import { fetchUpdateInfos } from '../fetchers/update-fetchers.js';
-import {
-  newEntryQueryInputValidator,
-  verifyCalendarQueryThreadIDs,
-} from '../responders/entry-responders.js';
+import { verifyCalendarQueryThreadIDs } from '../responders/entry-responders.js';
 import {
   fetchViewerForSocket,
   updateCookie,
@@ -105,7 +105,7 @@
         sessionID: t.maybe(t.String),
       }),
       sessionState: tShape({
-        calendarQuery: newEntryQueryInputValidator,
+        calendarQuery: calendarQueryValidator,
         messagesCurrentAsOf: t.Number,
         updatesCurrentAsOf: t.Number,
         watchedIDs: t.list(t.String),
diff --git a/lib/types/filter-types.js b/lib/types/filter-types.js
--- a/lib/types/filter-types.js
+++ b/lib/types/filter-types.js
@@ -22,10 +22,12 @@
 
 export const calendarFilterValidator: TUnion<CalendarFilter> = t.union([
   tShape<CalendarThreadFilter>({
-    type: tString('threads'),
+    type: tString(calendarThreadFilterTypes.THREAD_LIST),
     threadIDs: t.list(tID),
   }),
-  tShape<NotDeletedFilter>({ type: tString('not_deleted') }),
+  tShape<NotDeletedFilter>({
+    type: tString(calendarThreadFilterTypes.NOT_DELETED),
+  }),
 ]);
 
 export const defaultCalendarFilters: $ReadOnlyArray<CalendarFilter> = [