Add destination time difference and live local times on trip pages

Closes #208

templates/trip_page.html

@@ -99,6 +99,31 @@
     <div class="mb-3">
     {# <div>Countries: {{ trip.countries_str }}</div> #}
     <div>Locations: {{ trip.locations_str }}</div>
+    {% if destination_times %}
+      <div class="mt-2">
+        <strong>Destination time zones</strong>
+        <table class="table table-sm table-hover w-auto mb-0">
+          <thead>
+            <tr>
+              <th>Destination</th>
+              <th>Timezone</th>
+              <th>Difference from UK</th>
+              <th>Current local time</th>
+            </tr>
+          </thead>
+          <tbody>
+          {% for item in destination_times %}
+            <tr>
+              <td>{{ item.location }} ({{ item.country_name }}) {{ item.country_flag if trip.show_flags }}</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-time" {% if item.timezone %}data-timezone="{{ item.timezone }}"{% endif %}>{{ item.current_time or "Unknown" }}</td>
+            </tr>
+          {% endfor %}
+          </tbody>
+        </table>
+      </div>
+    {% endif %}
 
     {% if total_distance %}
       <div>Total distance:
@@ -465,5 +490,46 @@ var routes = {{ routes | tojson }};
 
 build_map("map", coordinates, routes);
 
+function timezoneOffsetLabel(offsetMinutes) {
+  if (offsetMinutes === 0) {
+    return "Same time as Bristol";
+  }
+  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;
+    el.textContent = new Intl.DateTimeFormat("en-GB", {
+      timeZone: tz,
+      weekday: "short",
+      hour: "2-digit",
+      minute: "2-digit",
+      second: "2-digit",
+      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();
+setInterval(updateDestinationTimes, 1000);
+
 </script>
 {% endblock %}

web_view.py

@@ -11,10 +11,13 @@ import os.path
 import sys
 import time
 import traceback
+import typing
 from collections import defaultdict
 from datetime import date, datetime, timedelta, timezone
+from zoneinfo import ZoneInfo
 
 import flask
+import pytz
 import werkzeug
 import werkzeug.debug.tbtools
 import yaml
@@ -761,6 +764,104 @@ def get_prev_current_and_next_trip(
     return (prev_trip, current_trip, next_trip)
 
 
+def _timezone_name_from_datetime(value: typing.Any) -> str | None:
+    """Get IANA timezone name from a datetime value if available."""
+    if not isinstance(value, datetime) or value.tzinfo is None:
+        return None
+
+    key = getattr(value.tzinfo, "key", None)
+    if isinstance(key, str):
+        return key
+
+    zone = getattr(value.tzinfo, "zone", None)
+    if isinstance(zone, str):
+        return zone
+
+    return None
+
+
+def _format_offset_from_bristol(offset_minutes: int) -> str:
+    """Format offset from Bristol in +/-HH:MM."""
+    if offset_minutes == 0:
+        return "Same time as Bristol"
+    sign = "+" if offset_minutes > 0 else "-"
+    hours, mins = divmod(abs(offset_minutes), 60)
+    return f"{sign}{hours:02d}:{mins:02d} vs Bristol"
+
+
+def get_destination_timezones(trip: Trip) -> list[StrDict]:
+    """Build destination timezone metadata for the trip page."""
+    per_location: dict[tuple[str, str], list[str]] = defaultdict(list)
+    for item in trip.accommodation + trip.conferences + trip.events:
+        location = item.get("location")
+        country = item.get("country")
+        if not isinstance(location, str) or not isinstance(country, str):
+            continue
+
+        key = (location, country.lower())
+        timezone_name = item.get("timezone")
+        if isinstance(timezone_name, str):
+            per_location[key].append(timezone_name)
+
+        for field in (
+            "from",
+            "to",
+            "date",
+            "start",
+            "end",
+            "attend_start",
+            "attend_end",
+        ):
+            candidate = _timezone_name_from_datetime(item.get(field))
+            if candidate:
+                per_location[key].append(candidate)
+
+    home_now = datetime.now(ZoneInfo("Europe/London"))
+    destination_times: list[StrDict] = []
+
+    for location, country in trip.locations():
+        country_code = country.alpha_2.lower()
+        key = (location, country_code)
+        timezone_name = None
+
+        for candidate in per_location.get(key, []):
+            try:
+                ZoneInfo(candidate)
+                timezone_name = candidate
+                break
+            except Exception:
+                continue
+
+        if not timezone_name:
+            country_timezones = pytz.country_timezones.get(country_code, [])
+            if len(country_timezones) == 1:
+                timezone_name = country_timezones[0]
+
+        offset_display = "Timezone unknown"
+        current_time = None
+        if timezone_name:
+            dest_now = datetime.now(ZoneInfo(timezone_name))
+            dest_offset = dest_now.utcoffset()
+            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)
+            current_time = dest_now.strftime("%a %H:%M:%S")
+
+        destination_times.append(
+            {
+                "location": location,
+                "country_name": country.name,
+                "country_flag": country.flag,
+                "timezone": timezone_name,
+                "offset_display": offset_display,
+                "current_time": current_time,
+            }
+        )
+
+    return destination_times
+
+
 @app.route("/trip/<start>")
 def trip_page(start: str) -> str:
     """Individual trip page."""
@@ -802,6 +903,7 @@ def trip_page(start: str) -> str:
         format_list_with_ampersand=format_list_with_ampersand,
         holidays=agenda.holidays.get_trip_holidays(trip),
         school_holidays=agenda.holidays.get_trip_school_holidays(trip),
+        destination_times=get_destination_timezones(trip),
         human_readable_delta=agenda.utils.human_readable_delta,
         trip_weather=trip_weather,
     )