Render UK time difference server-side and simplify trip timezone JS

templates/trip_page.html

@@ -114,9 +114,9 @@
           <tbody>
           {% for item in destination_times %}
             <tr>
-              <td>{{ item.location }} ({{ item.country_name }}) {{ item.country_flag if trip.show_flags }}</td>
+              <td>{{ item.destination_label }}</td>
               <td>{{ item.timezone or "Unknown" }}</td>
-              <td class="destination-offset" {% if item.timezone %}data-timezone="{{ item.timezone }}"{% endif %}>{{ item.offset_display }}</td>
+              <td class="destination-offset">{{ item.offset_display }}</td>
               <td class="destination-time" {% if item.timezone %}data-timezone="{{ item.timezone }}"{% endif %}>{{ item.current_time or "Unknown" }}</td>
             </tr>
           {% endfor %}
@@ -490,24 +490,6 @@ var routes = {{ routes | tojson }};
 
 build_map("map", coordinates, routes);
 
-function timezoneOffsetLabel(offsetMinutes) {
-  if (offsetMinutes === 0) {
-    return "No difference";
-  }
-  const sign = offsetMinutes > 0 ? "+" : "-";
-  const abs = Math.abs(offsetMinutes);
-  const hours = String(Math.floor(abs / 60)).padStart(2, "0");
-  const minutes = String(abs % 60).padStart(2, "0");
-  return `${sign}${hours}:${minutes} vs Bristol`;
-}
-
-function getOffsetMinutes(timeZone) {
-  const now = new Date();
-  const localInZone = new Date(now.toLocaleString("en-US", { timeZone }));
-  const localInBristol = new Date(now.toLocaleString("en-US", { timeZone: "Europe/London" }));
-  return Math.round((localInZone - localInBristol) / 60000);
-}
-
 function updateDestinationTimes() {
   for (const el of document.querySelectorAll(".destination-time[data-timezone]")) {
     const tz = el.dataset.timezone;
@@ -520,12 +502,6 @@ function updateDestinationTimes() {
       hour12: false
     }).format(new Date());
   }
-
-  for (const el of document.querySelectorAll(".destination-offset[data-timezone]")) {
-    const tz = el.dataset.timezone;
-    const offset = getOffsetMinutes(tz);
-    el.textContent = timezoneOffsetLabel(offset);
-  }
 }
 
 updateDestinationTimes();

web_view.py

@@ -781,13 +781,13 @@ def _timezone_name_from_datetime(value: typing.Any) -> str | None:
     return None
 
 
-def _format_offset_from_bristol(offset_minutes: int) -> str:
+def _format_offset_from_uk(offset_minutes: int) -> str:
-    """Format offset from Bristol in +/-HH:MM."""
+    """Format offset from UK in +/-HH:MM."""
     if offset_minutes == 0:
-        return "Same time as Bristol"
+        return "No difference"
     sign = "+" if offset_minutes > 0 else "-"
     hours, mins = divmod(abs(offset_minutes), 60)
-    return f"{sign}{hours:02d}:{mins:02d} vs Bristol"
+    return f"{sign}{hours:02d}:{mins:02d} vs UK"
 
 
 def _timezone_from_coordinates(latitude: float, longitude: float) -> str | None:
@@ -888,7 +888,7 @@ def get_destination_timezones(trip: Trip) -> list[StrDict]:
             home_offset = home_now.utcoffset()
             if dest_offset is not None and home_offset is not None:
                 offset_minutes = int((dest_offset - home_offset).total_seconds() // 60)
-                offset_display = _format_offset_from_bristol(offset_minutes)
+                offset_display = _format_offset_from_uk(offset_minutes)
             current_time = dest_now.strftime("%a %H:%M:%S")
 
         destination_times.append(
@@ -902,7 +902,41 @@ def get_destination_timezones(trip: Trip) -> list[StrDict]:
             }
         )
 
-    return destination_times
+    grouped: list[StrDict] = []
+    grouped_index: dict[tuple[str, str, str | None], int] = {}
+    for item in destination_times:
+        key = (item["country_name"], item["country_flag"], item["timezone"])
+        if key in grouped_index:
+            existing = grouped[grouped_index[key]]
+            existing_locations = typing.cast(list[str], existing["locations"])
+            existing_locations.append(typing.cast(str, item["location"]))
+            existing["location_count"] = (
+                typing.cast(int, existing["location_count"]) + 1
+            )
+            continue
+
+        grouped_index[key] = len(grouped)
+        grouped.append(
+            {
+                **item,
+                "locations": [item["location"]],
+                "location_count": 1,
+            }
+        )
+
+    for item in grouped:
+        location_count = typing.cast(int, item["location_count"])
+        country_name = typing.cast(str, item["country_name"])
+        country_flag = typing.cast(str, item["country_flag"])
+        if location_count > 1:
+            label = f"{country_name} ({location_count} locations)"
+        else:
+            label = f"{item['location']} ({country_name})"
+        if trip.show_flags:
+            label = f"{label} {country_flag}"
+        item["destination_label"] = label
+
+    return grouped
 
 
 @app.route("/trip/<start>")