Fix online board details date selection

src/features/online-board/components/FlightsMiniList/FlightsMiniListItem.tsx

@@ -12,6 +12,7 @@ import { Link } from "@modern-js/runtime/router";
 import { useTranslation } from "@/i18n/provider.js";
 import type { ISimpleFlight, IFlightLeg } from "../../types.js";
 import { buildOnlineBoardUrl } from "../../url.js";
+import { getFlightSearchDate } from "../../flightSearchDate.js";
 import {
   formatLocalTime,
   formatDayMonthYear,
@@ -51,7 +52,7 @@ export const FlightsMiniListItem = forwardRef<HTMLAnchorElement, FlightsMiniList
       carrier: flight.flightId.carrier,
       flightNumber: flight.flightId.flightNumber,
       ...(flight.flightId.suffix ? { suffix: flight.flightId.suffix } : {}),
-      date: flight.flightId.date,
+      date: getFlightSearchDate(flight),
     })}`;
 
     const depIso = getDepTimeIso(dep);

src/features/online-board/components/OnlineBoardDetailsPage.tsx

@@ -22,6 +22,7 @@ import { useOnlineBoard } from "../hooks/useOnlineBoard.js";
 import { parseDetailsRequestParam } from "@/shared/detailsRequestParam.js";
 import { buildFlightJsonLd } from "../json-ld.js";
 import { buildOnlineBoardUrl } from "../url.js";
+import { getFlightSearchDate } from "../flightSearchDate.js";
 import { useCityName, useStationDisplayName } from "@/shared/hooks/useDictionaries.js";
 import { FlightDetailsAccordion } from "./details-panels/FlightDetailsAccordion.js";
 import { FlightsMiniList } from "./FlightsMiniList/index.js";
@@ -388,9 +389,9 @@ export const OnlineBoardDetailsPage: FC<OnlineBoardDetailsPageProps> = ({
 
   // Pick the flight matching the URL's flightId (date-based match). The API
   // response may contain multiple flights with the same flight number on
-  // different dates; we need the one the user actually navigated to.
+  // different dates; match Angular's dateToSearchBy, not backend flightId.date.
   const flight =
-    allFlights.find((f) => f.flightId.date === flightId.date) ?? firstFlight;
+    allFlights.find((f) => getFlightSearchDate(f) === flightId.date) ?? firstFlight;
 
   // Live updates via SignalR
   const { flight: liveFlight, connectionStatus } = useLiveFlightDetails(

src/features/online-board/components/OnlineBoardSearchPage.tsx

@@ -36,6 +36,7 @@ import { useCalendarDays } from "../hooks/useCalendarDays.js";
 import { buildOnlineBoardUrl } from "../url.js";
 import { buildFlightListJsonLd } from "../json-ld.js";
 import { sortFlights } from "../sortFlights.js";
+import { getFlightSearchDate } from "../flightSearchDate.js";
 import {
   PobedaAuroraBanner,
   shouldShowPobedaAuroraBanner,
@@ -388,13 +389,13 @@ export const OnlineBoardSearchPage: FC<OnlineBoardSearchPageProps> = ({
             carrier: flight.flightId.carrier,
             flightNumber: flight.flightId.flightNumber,
             suffix: flight.flightId.suffix,
-            date: flight.flightId.date,
+            date: getFlightSearchDate(flight),
           }
         : {
             type: "details",
             carrier: flight.flightId.carrier,
             flightNumber: flight.flightId.flightNumber,
-            date: flight.flightId.date,
+            date: getFlightSearchDate(flight),
           };
       const detailsUrl = buildOnlineBoardUrl(detailsParams);
       void navigate(`/${locale}/${detailsUrl}`);

src/features/online-board/flightSearchDate.test.ts

@@ -0,0 +1,113 @@
+import { describe, expect, it } from "vitest";
+import { getFlightSearchDate } from "./flightSearchDate.js";
+import type { IDirectFlight, IMultiLegFlight, IFlightLeg } from "./types.js";
+
+function leg(local: string): IFlightLeg {
+  return {
+    arrival: {
+      scheduled: { airport: "", airportCode: "", city: "", cityCode: "", countryCode: "" },
+      times: {
+        scheduledArrival: {
+          dayChange: { value: 0, title: "" },
+          local,
+          localTime: "",
+          tzOffset: 0,
+          utc: "",
+        },
+      },
+    },
+    dayChange: 0,
+    departure: {
+      scheduled: { airport: "", airportCode: "", city: "", cityCode: "", countryCode: "" },
+      checkingStatus: "Scheduled",
+      times: {
+        scheduledDeparture: {
+          dayChange: { value: 0, title: "" },
+          local,
+          localTime: "",
+          tzOffset: 0,
+          utc: "",
+        },
+      },
+    },
+    equipment: {},
+    flags: { checkinAvailable: false, returnToAirport: false, routeChanged: false },
+    flyingTime: "",
+    index: 0,
+    operatingBy: {},
+    status: "Scheduled",
+    updated: "",
+  };
+}
+
+describe("getFlightSearchDate", () => {
+  it("uses scheduled local departure date instead of backend flightId.date", () => {
+    const flight: IDirectFlight = {
+      id: "SU6951",
+      routeType: "Direct",
+      flyingTime: "",
+      operatingBy: {},
+      status: "Arrived",
+      flightId: {
+        carrier: "SU",
+        flightNumber: "6951",
+        suffix: "",
+        date: "2026-05-04",
+        dateLT: "2026-05-05",
+      },
+      leg: leg("2026-05-05T00:30:00+03:00"),
+    };
+
+    expect(getFlightSearchDate(flight)).toBe("20260505");
+  });
+
+  it("uses the first leg for multi-leg flights", () => {
+    const flight: IMultiLegFlight = {
+      id: "SU100",
+      routeType: "MultiLeg",
+      flyingTime: "",
+      operatingBy: {},
+      status: "Scheduled",
+      flightId: {
+        carrier: "SU",
+        flightNumber: "0100",
+        suffix: "",
+        date: "20260504",
+      },
+      legs: [
+        leg("2026-05-05T23:30:00+03:00"),
+        leg("2026-05-06T01:30:00+03:00"),
+      ],
+    };
+
+    expect(getFlightSearchDate(flight)).toBe("20260505");
+  });
+
+  it("falls back to dateLT and then flightId.date when leg date is unavailable", () => {
+    const flight: IDirectFlight = {
+      id: "SU42",
+      routeType: "Direct",
+      flyingTime: "",
+      operatingBy: {},
+      status: "Scheduled",
+      flightId: {
+        carrier: "SU",
+        flightNumber: "0042",
+        suffix: "",
+        date: "2026-05-04",
+        dateLT: "2026-05-05",
+      },
+      leg: leg("10:00"),
+    };
+
+    expect(getFlightSearchDate(flight)).toBe("20260505");
+
+    const { dateLT: _dateLT, ...flightIdWithoutDateLt } = flight.flightId;
+    const withoutDateLt: IDirectFlight = {
+      ...flight,
+      flightId: flightIdWithoutDateLt,
+    };
+
+    expect(getFlightSearchDate(withoutDateLt)).toBe("20260504");
+  });
+});

src/features/online-board/flightSearchDate.ts

@@ -0,0 +1,34 @@
+import type { IFlightLeg, ISimpleFlight } from "./types.js";
+
+function compactDate(value: string | undefined): string | null {
+  if (!value) return null;
+  if (/^\d{8}$/.test(value)) return value;
+
+  const match = /^(\d{4})-(\d{2})-(\d{2})/.exec(value);
+  if (!match) return null;
+
+  return `${match[1]}${match[2]}${match[3]}`;
+}
+
+function getFirstLeg(flight: ISimpleFlight): IFlightLeg | null {
+  if (flight.routeType === "Direct") return flight.leg;
+  return flight.legs[0] ?? null;
+}
+
+/**
+ * Angular's FlightDateUtils.getFlightDate derives the details URL date from
+ * the first leg's scheduled local departure date, not from flightId.date.
+ * Overnight flights can have flightId.date set to the previous backend
+ * service day while dateLT / scheduled local departure belongs to the board
+ * day the user clicked.
+ */
+export function getFlightSearchDate(flight: ISimpleFlight): string {
+  const firstLeg = getFirstLeg(flight);
+
+  return (
+    compactDate(firstLeg?.departure.times.scheduledDeparture.local) ??
+    compactDate(flight.flightId.dateLT) ??
+    compactDate(flight.flightId.date) ??
+    flight.flightId.date.replace(/-/g, "")
+  );
+}