diff --git a/geneit_app/src/api/accommodations/AccommodationsReservationsApi.tsx b/geneit_app/src/api/accommodations/AccommodationsReservationsApi.tsx
index 845372a..7c426b9 100644
--- a/geneit_app/src/api/accommodations/AccommodationsReservationsApi.tsx
+++ b/geneit_app/src/api/accommodations/AccommodationsReservationsApi.tsx
@@ -1,5 +1,6 @@
 import { APIClient } from "../ApiClient";
 import { Family } from "../FamilyApi";
+import { Accommodation } from "./AccommodationListApi";
 
 export interface AccommodationReservation {
   id: number;
@@ -59,6 +60,7 @@ export interface UpdateAccommodationReservation {
   start: number;
   end: number;
   accommodation_id: number;
+  reservation_id?: number;
 }
 
 export class AccommodationsReservationsApi {
@@ -77,4 +79,23 @@ export class AccommodationsReservationsApi {
 
     return new AccommodationsReservationsList(data);
   }
+
+  /**
+   * Get the reservations of a given time interval for an accommodation
+   */
+  static async ReservationsForInterval(
+    family: Family,
+    accommodation: Accommodation,
+    start: number,
+    end: number
+  ): Promise<AccommodationsReservationsList> {
+    const data = (
+      await APIClient.exec({
+        method: "GET",
+        uri: `/family/${family.family_id}/accommodations/reservations/accommodation/${accommodation.id}/for_interval?start=${start}&end=${end}`,
+      })
+    ).data;
+
+    return new AccommodationsReservationsList(data);
+  }
 }
diff --git a/geneit_app/src/dialogs/accommodations/UpdateReservationDialog.tsx b/geneit_app/src/dialogs/accommodations/UpdateReservationDialog.tsx
index 362d608..3ac396a 100644
--- a/geneit_app/src/dialogs/accommodations/UpdateReservationDialog.tsx
+++ b/geneit_app/src/dialogs/accommodations/UpdateReservationDialog.tsx
@@ -1,15 +1,24 @@
 import {
+  Alert,
   Button,
   Dialog,
   DialogActions,
   DialogContent,
   DialogTitle,
+  Typography,
 } from "@mui/material";
 import React from "react";
-import { UpdateAccommodationReservation } from "../../api/accommodations/AccommodationsReservationsApi";
+import {
+  AccommodationReservation,
+  AccommodationsReservationsApi,
+  UpdateAccommodationReservation,
+} from "../../api/accommodations/AccommodationsReservationsApi";
+import { useAlert } from "../../hooks/context_providers/AlertDialogProvider";
+import { useFamily } from "../../widgets/BaseFamilyRoute";
 import { useAccommodations } from "../../widgets/accommodations/BaseAccommodationsRoute";
 import { PropDateInput } from "../../widgets/forms/PropDateInput";
 import { PropSelect } from "../../widgets/forms/PropSelect";
+import { fmtUnixDate } from "../../utils/time_utils";
 
 export function UpdateReservationDialog(p: {
   open: boolean;
@@ -18,12 +27,19 @@ export function UpdateReservationDialog(p: {
   onClose: () => void;
   onSubmitted: (c: UpdateAccommodationReservation) => void;
 }): React.ReactElement {
+  const alert = useAlert();
+
+  const family = useFamily();
   const accommodations = useAccommodations();
 
   const [reservation, setReservation] = React.useState<
     UpdateAccommodationReservation | undefined
   >();
 
+  const [conflicts, setConflicts] = React.useState<
+    AccommodationReservation[] | undefined
+  >(undefined);
+
   const clearForm = () => {
     setReservation(undefined);
   };
@@ -42,7 +58,46 @@ export function UpdateReservationDialog(p: {
     if (!reservation) setReservation(p.reservation);
   }, [p.open, p.reservation]);
 
-  // TODO : check availability
+  React.useEffect(() => {
+    setConflicts(undefined);
+    (async () => {
+      try {
+        if (
+          !reservation ||
+          reservation.accommodation_id < 1 ||
+          reservation.start < 1 ||
+          reservation.start > reservation.end
+        ) {
+          setConflicts([]);
+          return;
+        }
+
+        setConflicts(
+          (
+            await AccommodationsReservationsApi.ReservationsForInterval(
+              family.family,
+              accommodations.accommodations.get(reservation.accommodation_id)!,
+              reservation.start,
+              reservation.end
+            )
+          ).filter(
+            (r) =>
+              r.id !== p.reservation?.reservation_id && r.validated !== false
+          )
+        );
+      } catch (e) {
+        console.error(e);
+        alert(
+          "Echec de la vérification de la présence de conflits de calendrier !"
+        );
+      }
+    })();
+  }, [
+    p.open,
+    reservation?.accommodation_id,
+    reservation?.start,
+    reservation?.end,
+  ]);
 
   return (
     <Dialog open={p.open} onClose={cancel}>
@@ -94,7 +149,22 @@ export function UpdateReservationDialog(p: {
           minDate={reservation?.start}
         />
 
-        {/* TODO : la suite */}
+        {conflicts && conflicts.length > 0 && (
+          <Alert severity="error">
+            <p>
+              Cette réservation est en conflit avec d'autres réservations sur
+              les intervalles suivants :
+            </p>
+            <ul>
+              {conflicts.map((c, num) => (
+                <li key={num}>
+                  Réservation du {fmtUnixDate(c.reservation_start)} au{" "}
+                  {fmtUnixDate(c.reservation_end)}
+                </li>
+              ))}
+            </ul>
+          </Alert>
+        )}
       </DialogContent>
       <DialogActions>
         <Button onClick={cancel}>Annuler</Button>
@@ -104,7 +174,8 @@ export function UpdateReservationDialog(p: {
             !(
               (reservation?.accommodation_id ?? -1) > 0 &&
               (reservation?.start ?? -1) > 0 &&
-              (reservation?.end ?? -1) > (reservation?.start ?? 0)
+              (reservation?.end ?? -1) > (reservation?.start ?? 0) &&
+              (conflicts?.length ?? 0) === 0
             )
           }
         >
diff --git a/geneit_app/src/routes/family/accommodations/AccommodationsReservationsRoute.tsx b/geneit_app/src/routes/family/accommodations/AccommodationsReservationsRoute.tsx
index 5d979a8..324f9bd 100644
--- a/geneit_app/src/routes/family/accommodations/AccommodationsReservationsRoute.tsx
+++ b/geneit_app/src/routes/family/accommodations/AccommodationsReservationsRoute.tsx
@@ -74,7 +74,7 @@ export function AccommodationsReservationsRoute(): React.ReactElement {
 
   return (
     <>
-      <FamilyPageTitle title="Réservation" />
+      <FamilyPageTitle title="Réservations" />
       <AsyncWidget
         loadKey={loadKey.current}
         load={load}
diff --git a/geneit_app/src/widgets/forms/PropDateInput.tsx b/geneit_app/src/widgets/forms/PropDateInput.tsx
index 732afbe..da8fefc 100644
--- a/geneit_app/src/widgets/forms/PropDateInput.tsx
+++ b/geneit_app/src/widgets/forms/PropDateInput.tsx
@@ -39,23 +39,22 @@ export function PropDateInput(p: {
   const maxDate = p.maxDate ? dayjs(new Date(p.maxDate * 1000)) : undefined;
 
   return (
-    <div style={{ margin: "10px auto" }}>
-      <LocalizationProvider dateAdapter={AdapterDayjs} adapterLocale="fr">
-        <DatePicker
-          label={p.label}
-          value={value}
-          onChange={(v) => {
-            if (v && p.lastSecOfDay) {
-              v.set("hours", 23);
-              v.set("minutes", 59);
-              v.set("seconds", 59);
-            }
-            p.onChange?.(v ? v.unix() : undefined);
-          }}
-          minDate={minDate}
-          maxDate={maxDate}
-        />
-      </LocalizationProvider>
-    </div>
+    <LocalizationProvider dateAdapter={AdapterDayjs} adapterLocale="fr">
+      <DatePicker
+        label={p.label}
+        value={value}
+        onChange={(v) => {
+          if (v && p.lastSecOfDay) {
+            v.set("hours", 23);
+            v.set("minutes", 59);
+            v.set("seconds", 59);
+          }
+          p.onChange?.(v ? v.unix() : undefined);
+        }}
+        minDate={minDate}
+        maxDate={maxDate}
+      />
+      <div style={{ height: "10px" }}></div>
+    </LocalizationProvider>
   );
 }
diff --git a/geneit_backend/src/controllers/accommodations_reservations_controller.rs b/geneit_backend/src/controllers/accommodations_reservations_controller.rs
index bda86ca..8c3fba5 100644
--- a/geneit_backend/src/controllers/accommodations_reservations_controller.rs
+++ b/geneit_backend/src/controllers/accommodations_reservations_controller.rs
@@ -93,6 +93,31 @@ pub async fn get_accommodation_reservations(a: FamilyAndAccommodationInPath) ->
         .json(accommodations_reservations_service::get_all_of_accommodation(a.id()).await?))
 }
 
+#[derive(serde::Deserialize)]
+pub struct CheckAvailabilityQuery {
+    start: usize,
+    end: usize,
+}
+
+/// Check reservation availability
+pub async fn get_accommodation_reservations_for_interval(
+    a: FamilyAndAccommodationInPath,
+    req: web::Query<CheckAvailabilityQuery>,
+) -> HttpResult {
+    if req.start > req.end {
+        return Ok(HttpResponse::BadRequest().json("start should be smaller than end!"));
+    }
+
+    let res = accommodations_reservations_service::get_reservations_for_time_interval(
+        a.id(),
+        req.start,
+        req.end,
+    )
+    .await?;
+
+    Ok(HttpResponse::Ok().json(res))
+}
+
 /// Get the full list of accommodations reservations for a family
 pub async fn full_list(m: FamilyInPath) -> HttpResult {
     Ok(HttpResponse::Ok()
diff --git a/geneit_backend/src/main.rs b/geneit_backend/src/main.rs
index ff815fc..b4b0f74 100644
--- a/geneit_backend/src/main.rs
+++ b/geneit_backend/src/main.rs
@@ -233,6 +233,11 @@ async fn main() -> std::io::Result<()> {
                 web::get()
                     .to(accommodations_reservations_controller::get_accommodation_reservations),
             )
+            .route(
+                "/family/{id}/accommodations/reservations/accommodation/{accommodation_id}/for_interval",
+                web::get()
+                    .to(accommodations_reservations_controller::get_accommodation_reservations_for_interval),
+            )
             .route(
                 "/family/{id}/accommodations/reservations/full_list",
                 web::get().to(accommodations_reservations_controller::full_list),