migrate stored TZ formats from IANA labels on boot

interface/src/app/settings/NTPSettings.tsx

@@ -1,4 +1,4 @@
-import { useState } from 'react';
+import { useEffect, useRef, useState } from 'react';
 
 import AccessTimeIcon from '@mui/icons-material/AccessTime';
 import CancelIcon from '@mui/icons-material/Cancel';
@@ -42,6 +42,7 @@ import type { ValidateFieldsError } from 'validators/schema';
 
 import {
   TIME_ZONES,
+  migrateNtpTimeZones,
   selectedTimeZone,
   timeZoneSelectItemsT,
   useTimeZoneSelectItems
@@ -56,6 +57,7 @@ const NTPSettings = () => {
     origData,
     dirtyFlags,
     setDirtyFlags,
+    setOrigData,
     blocker,
     saveData,
     errorMessage
@@ -81,6 +83,31 @@ const NTPSettings = () => {
   const [settingTime, setSettingTime] = useState<boolean>(false);
   const [processing, setProcessing] = useState<boolean>(false);
   const [fieldErrors, setFieldErrors] = useState<ValidateFieldsError>();
+  const migratingTz = useRef(false);
+
+  // If firmware has not yet rewritten tz_format from the label (or the user
+  // landed here before reboot), persist the current TIME_ZONES values quietly.
+  useEffect(() => {
+    if (!data || migratingTz.current || dirtyFlags.length > 0) {
+      return;
+    }
+    const migrated = migrateNtpTimeZones(data);
+    if (!migrated) {
+      return;
+    }
+    migratingTz.current = true;
+    void (async () => {
+      try {
+        updateDataValue(migrated);
+        await NTPApi.updateNTPSettings(migrated);
+        setOrigData(migrated);
+      } catch {
+        // Boot-time firmware migration still applies on the next restart.
+      } finally {
+        migratingTz.current = false;
+      }
+    })();
+  }, [data, dirtyFlags.length, setOrigData, updateDataValue]);
 
   const { send: updateTime } = useRequest(
     (local_time: Time) => NTPApi.updateTime(local_time),

interface/src/app/settings/TZ.tsx

@@ -466,8 +466,39 @@ export const TIME_ZONES: Record<string, string> = {
 // Pre-compute sorted timezone labels for better performance
 export const TIME_ZONE_LABELS = Object.keys(TIME_ZONES).sort();
 
+/** Resolve the select value for a saved zone. Prefer the label when it is in
+ * TIME_ZONES so a stale stored tz_format (after a table update) still shows the
+ * correct city; firmware migrates the format from the label on boot. */
 export function selectedTimeZone(label: string, format: string) {
-  return TIME_ZONES[label] === format ? label : undefined;
+  if (label in TIME_ZONES) {
+    return label;
+  }
+  return Object.keys(TIME_ZONES).find((key) => TIME_ZONES[key] === format);
+}
+
+/** Return settings with tz_format / tz_format_t refreshed from TIME_ZONES, or
+ * null if already current (or labels are unknown). */
+export function migrateNtpTimeZones<
+  T extends {
+    tz_label: string;
+    tz_format: string;
+    tz_label_t: string;
+    tz_format_t: string;
+  }
+>(settings: T): T | null {
+  const tz_format = TIME_ZONES[settings.tz_label];
+  const tz_format_t = TIME_ZONES[settings.tz_label_t];
+  const next = { ...settings };
+  let changed = false;
+  if (tz_format && tz_format !== settings.tz_format) {
+    next.tz_format = tz_format;
+    changed = true;
+  }
+  if (tz_format_t && tz_format_t !== settings.tz_format_t) {
+    next.tz_format_t = tz_format_t;
+    changed = true;
+  }
+  return changed ? next : null;
 }
 
 const precomputedTimeZoneItems = TIME_ZONE_LABELS.map((label) => (

scripts/generate_tz_zones.py

@@ -0,0 +1,83 @@
+#!/usr/bin/env python3
+"""Generate src/ESP32React/tz_zones.h from interface/src/app/settings/TZ.tsx.
+
+Run from the repo root:
+  python3 scripts/generate_tz_zones.py
+"""
+
+from __future__ import annotations
+
+import re
+import sys
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+TZ_TSX = ROOT / "interface" / "src" / "app" / "settings" / "TZ.tsx"
+OUT_H = ROOT / "src" / "ESP32React" / "tz_zones.h"
+
+
+def parse_time_zones(text: str) -> list[tuple[str, str]]:
+    match = re.search(
+        r"export const TIME_ZONES: Record<string, string> = \{([\s\S]*?)\n\};",
+        text,
+    )
+    if not match:
+        raise SystemExit("TIME_ZONES table not found in TZ.tsx")
+    entries = re.findall(r"'((?:\\'|[^'])*)': '((?:\\'|[^'])*)'", match.group(1))
+    if not entries:
+        raise SystemExit("no TIME_ZONES entries parsed")
+    return sorted(entries, key=lambda item: item[0])
+
+
+def c_string(value: str) -> str:
+    return '"' + value.replace("\\", "\\\\").replace('"', '\\"') + '"'
+
+
+def main() -> int:
+    entries = parse_time_zones(TZ_TSX.read_text(encoding="utf-8"))
+    max_format = max(len(fmt) for _, fmt in entries)
+
+    lines = [
+        "/* Auto-generated by scripts/generate_tz_zones.py — do not edit. */",
+        "#pragma once",
+        "",
+        "#include <stdlib.h>",
+        "#include <string.h>",
+        "",
+        "struct EmsespTzZone {",
+        "    const char * label;",
+        "    const char * format;",
+        "};",
+        "",
+        f"// Longest POSIX TZ value in the table is {max_format} chars.",
+        "static constexpr size_t EMSESP_TZ_ZONE_COUNT = "
+        f"{len(entries)};",
+        "static const EmsespTzZone EMSESP_TZ_ZONES[EMSESP_TZ_ZONE_COUNT] = {",
+    ]
+    for label, fmt in entries:
+        lines.append(f"    {{{c_string(label)}, {c_string(fmt)}}},")
+    lines += [
+        "};",
+        "",
+        "inline int emsesp_tz_zone_cmp(const void * key, const void * element) {",
+        "    return strcmp(static_cast<const char *>(key), static_cast<const EmsespTzZone *>(element)->label);",
+        "}",
+        "",
+        "// Returns the POSIX TZ string for an IANA label, or nullptr if unknown.",
+        "inline const char * emsesp_tz_format_for_label(const char * label) {",
+        "    if (label == nullptr || *label == '\\0') {",
+        "        return nullptr;",
+        "    }",
+        "    const auto * found = static_cast<const EmsespTzZone *>(",
+        "        bsearch(label, EMSESP_TZ_ZONES, EMSESP_TZ_ZONE_COUNT, sizeof(EmsespTzZone), emsesp_tz_zone_cmp));",
+        "    return found != nullptr ? found->format : nullptr;",
+        "}",
+        "",
+    ]
+    OUT_H.write_text("\n".join(lines), encoding="utf-8")
+    print(f"Wrote {OUT_H.relative_to(ROOT)} ({len(entries)} zones, max format {max_format})")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())

src/ESP32React/NTPSettingsService.cpp

@@ -1,7 +1,25 @@
 #include "NTPSettingsService.h"
 
+#include "tz_zones.h"
+
 #include <emsesp.h>
 
+namespace {
+
+String trimmedTzFormat(const String & format) {
+    int space = format.indexOf(' ');
+    return space < 0 ? format : format.substring(0, static_cast<unsigned int>(space));
+}
+
+void padTzFormat(String & format) {
+    format.reserve(NTP_TZ_FORMAT_LEN);
+    while (format.length() < NTP_TZ_FORMAT_LEN) {
+        format += ' ';
+    }
+}
+
+} // namespace
+
 NTPSettingsService::NTPSettingsService(AsyncWebServer * server, FS * fs, SecurityManager * securityManager)
     : _httpEndpoint(NTPSettings::read, NTPSettings::update, this, server, NTP_SETTINGS_SERVICE_PATH, securityManager)
     , _fsPersistence(NTPSettings::read, NTPSettings::update, this, fs, NTP_SETTINGS_FILE)
@@ -16,6 +34,13 @@ NTPSettingsService::NTPSettingsService(AsyncWebServer * server, FS * fs, Securit
 
 void NTPSettingsService::begin() {
     _fsPersistence.readFromFS();
+
+    // After an OTA that updates tz_zones.h, rewrite stored POSIX strings from the
+    // saved IANA labels so localtime / thermostat sync use the current rules
+    // without the user re-selecting the zone in the WebUI.
+    update([](NTPSettings & settings) {
+        return NTPSettings::syncFormatsFromLabels(settings) ? StateUpdateResult::CHANGED : StateUpdateResult::UNCHANGED;
+    });
 }
 
 void NTPSettingsService::loop() {
@@ -77,15 +102,40 @@ void NTPSettings::read(NTPSettings & settings, JsonObject root) {
     root["enabled"]         = settings.enabled;
     root["server"]          = settings.server;
     root["tz_label"]        = settings.tzLabel;
-    root["tz_format"]       = settings.tzFormat.substring(0, settings.tzFormat.indexOf(" "));
+    root["tz_format"]       = trimmedTzFormat(settings.tzFormat);
     root["thermostat_sync"] = settings.thermostat_sync;
     root["tz_label_t"]      = settings.tzLabelT;
-    root["tz_format_t"]     = settings.tzFormatT.substring(0, settings.tzFormatT.indexOf(" "));
+    root["tz_format_t"]     = trimmedTzFormat(settings.tzFormatT);
+}
+
+bool NTPSettings::syncFormatsFromLabels(NTPSettings & settings) {
+    bool changed = false;
+
+    auto apply = [&](const String & label, String & format) {
+        const char * mapped = emsesp_tz_format_for_label(label.c_str());
+        if (mapped == nullptr) {
+            return;
+        }
+        if (trimmedTzFormat(format) == mapped) {
+            // Still re-pad in case NTP_TZ_FORMAT_LEN grew since the value was stored.
+            if (format.length() != NTP_TZ_FORMAT_LEN) {
+                format = mapped;
+                padTzFormat(format);
+                changed = true;
+            }
+            return;
+        }
+        format = mapped;
+        padTzFormat(format);
+        changed = true;
+    };
+
+    apply(settings.tzLabel, settings.tzFormat);
+    apply(settings.tzLabelT, settings.tzFormatT);
+    return changed;
 }
 
 StateUpdateResult NTPSettings::update(JsonObject root, NTPSettings & settings) {
-    settings.tzFormat.reserve(40);
-    settings.tzFormatT.reserve(40);
     settings.enabled         = root["enabled"] | FACTORY_NTP_ENABLED;
     settings.server          = root["server"] | FACTORY_NTP_SERVER;
     settings.tzLabel         = root["tz_label"] | FACTORY_NTP_TIME_ZONE_LABEL;
@@ -93,14 +143,15 @@ StateUpdateResult NTPSettings::update(JsonObject root, NTPSettings & settings) {
     settings.thermostat_sync = root["thermostat_sync"] | FACTORY_NTP_THERMOSTAT_SYNC;
     settings.tzLabelT        = root["tz_label_t"] | FACTORY_NTP_TIME_ZONE_LABEL;
     settings.tzFormatT       = root["tz_format_t"] | FACTORY_NTP_TIME_ZONE_FORMAT;
-    // The format string must have same length to avoid memory leak, #3184
-    while (settings.tzFormat.length() < 40) {
-        settings.tzFormat += " ";
-    }
 
-    while (settings.tzFormatT.length() < 40) {
+    // Do not call syncFormatsFromLabels here: readFromFS() uses this updater
-        settings.tzFormatT += " ";
+    // via updateWithoutPropagation, and a sync at that point would not be
-    }
+    // written back. Boot migration runs in NTPSettingsService::begin() instead.
+    // The WebUI always POSTs tz_format from TIME_ZONES when the user saves.
+
+    // The format string must have a fixed length to avoid a setenv leak, #3184.
+    padTzFormat(settings.tzFormat);
+    padTzFormat(settings.tzFormatT);
 
     return StateUpdateResult::CHANGED;
 }

src/ESP32React/NTPSettingsService.h

@@ -32,6 +32,12 @@
 #define NTP_SETTINGS_SERVICE_PATH "/rest/ntpSettings"
 #define TIME_PATH "/rest/time"
 
+// Fixed length for tz_format passed to setenv to avoid the realloc leak in #3184.
+// Must be >= longest POSIX TZ string in tz_zones.h (currently 44 for Pacific/Chatham).
+#ifndef NTP_TZ_FORMAT_LEN
+#define NTP_TZ_FORMAT_LEN 48
+#endif
+
 class NTPSettings {
   public:
     bool    enabled         = FACTORY_NTP_ENABLED;
@@ -44,6 +50,10 @@ class NTPSettings {
 
     static void              read(NTPSettings & settings, JsonObject root);
     static StateUpdateResult update(JsonObject root, NTPSettings & settings);
+
+    // Refresh tz_format / tz_format_t from the IANA label using tz_zones.h.
+    // Returns true if either format string changed.
+    static bool syncFormatsFromLabels(NTPSettings & settings);
 };
 
 class NTPSettingsService : public StatefulService<NTPSettings> {

src/ESP32React/tz_zones.h

@@ -0,0 +1,489 @@
+/* Auto-generated by scripts/generate_tz_zones.py — do not edit. */
+#pragma once
+
+#include <stdlib.h>
+#include <string.h>
+
+struct EmsespTzZone {
+    const char * label;
+    const char * format;
+};
+
+// Longest POSIX TZ value in the table is 44 chars.
+static constexpr size_t EMSESP_TZ_ZONE_COUNT = 460;
+static const EmsespTzZone EMSESP_TZ_ZONES[EMSESP_TZ_ZONE_COUNT] = {
+    {"Africa/Abidjan", "GMT0"},
+    {"Africa/Accra", "GMT0"},
+    {"Africa/Addis_Ababa", "EAT-3"},
+    {"Africa/Algiers", "CET-1"},
+    {"Africa/Asmara", "EAT-3"},
+    {"Africa/Bamako", "GMT0"},
+    {"Africa/Bangui", "WAT-1"},
+    {"Africa/Banjul", "GMT0"},
+    {"Africa/Bissau", "GMT0"},
+    {"Africa/Blantyre", "CAT-2"},
+    {"Africa/Brazzaville", "WAT-1"},
+    {"Africa/Bujumbura", "CAT-2"},
+    {"Africa/Cairo", "EET-2EEST,M4.5.5/0,M10.5.4/24"},
+    {"Africa/Casablanca", "<+00>0"},
+    {"Africa/Ceuta", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Africa/Conakry", "GMT0"},
+    {"Africa/Dakar", "GMT0"},
+    {"Africa/Dar_es_Salaam", "EAT-3"},
+    {"Africa/Djibouti", "EAT-3"},
+    {"Africa/Douala", "WAT-1"},
+    {"Africa/El_Aaiun", "<+00>0"},
+    {"Africa/Freetown", "GMT0"},
+    {"Africa/Gaborone", "CAT-2"},
+    {"Africa/Harare", "CAT-2"},
+    {"Africa/Johannesburg", "SAST-2"},
+    {"Africa/Juba", "CAT-2"},
+    {"Africa/Kampala", "EAT-3"},
+    {"Africa/Khartoum", "CAT-2"},
+    {"Africa/Kigali", "CAT-2"},
+    {"Africa/Kinshasa", "WAT-1"},
+    {"Africa/Lagos", "WAT-1"},
+    {"Africa/Libreville", "WAT-1"},
+    {"Africa/Lome", "GMT0"},
+    {"Africa/Luanda", "WAT-1"},
+    {"Africa/Lubumbashi", "CAT-2"},
+    {"Africa/Lusaka", "CAT-2"},
+    {"Africa/Malabo", "WAT-1"},
+    {"Africa/Maputo", "CAT-2"},
+    {"Africa/Maseru", "SAST-2"},
+    {"Africa/Mbabane", "SAST-2"},
+    {"Africa/Mogadishu", "EAT-3"},
+    {"Africa/Monrovia", "GMT0"},
+    {"Africa/Nairobi", "EAT-3"},
+    {"Africa/Ndjamena", "WAT-1"},
+    {"Africa/Niamey", "WAT-1"},
+    {"Africa/Nouakchott", "GMT0"},
+    {"Africa/Ouagadougou", "GMT0"},
+    {"Africa/Porto-Novo", "WAT-1"},
+    {"Africa/Sao_Tome", "GMT0"},
+    {"Africa/Tripoli", "EET-2"},
+    {"Africa/Tunis", "CET-1"},
+    {"Africa/Windhoek", "CAT-2"},
+    {"America/Adak", "HST10HDT,M3.2.0,M11.1.0"},
+    {"America/Anchorage", "AKST9AKDT,M3.2.0,M11.1.0"},
+    {"America/Anguilla", "AST4"},
+    {"America/Antigua", "AST4"},
+    {"America/Araguaina", "<-03>3"},
+    {"America/Argentina/Buenos_Aires", "<-03>3"},
+    {"America/Argentina/Catamarca", "<-03>3"},
+    {"America/Argentina/Cordoba", "<-03>3"},
+    {"America/Argentina/Jujuy", "<-03>3"},
+    {"America/Argentina/La_Rioja", "<-03>3"},
+    {"America/Argentina/Mendoza", "<-03>3"},
+    {"America/Argentina/Rio_Gallegos", "<-03>3"},
+    {"America/Argentina/Salta", "<-03>3"},
+    {"America/Argentina/San_Juan", "<-03>3"},
+    {"America/Argentina/San_Luis", "<-03>3"},
+    {"America/Argentina/Tucuman", "<-03>3"},
+    {"America/Argentina/Ushuaia", "<-03>3"},
+    {"America/Aruba", "AST4"},
+    {"America/Asuncion", "<-03>3"},
+    {"America/Atikokan", "EST5"},
+    {"America/Bahia", "<-03>3"},
+    {"America/Bahia_Banderas", "CST6"},
+    {"America/Barbados", "AST4"},
+    {"America/Belem", "<-03>3"},
+    {"America/Belize", "CST6"},
+    {"America/Blanc-Sablon", "AST4"},
+    {"America/Boa_Vista", "<-04>4"},
+    {"America/Bogota", "<-05>5"},
+    {"America/Boise", "MST7MDT,M3.2.0,M11.1.0"},
+    {"America/Cambridge_Bay", "MST7MDT,M3.2.0,M11.1.0"},
+    {"America/Campo_Grande", "<-04>4"},
+    {"America/Cancun", "EST5"},
+    {"America/Caracas", "<-04>4"},
+    {"America/Cayenne", "<-03>3"},
+    {"America/Cayman", "EST5"},
+    {"America/Chicago", "CST6CDT,M3.2.0,M11.1.0"},
+    {"America/Chihuahua", "CST6"},
+    {"America/Costa_Rica", "CST6"},
+    {"America/Creston", "MST7"},
+    {"America/Cuiaba", "<-04>4"},
+    {"America/Curacao", "AST4"},
+    {"America/Danmarkshavn", "GMT0"},
+    {"America/Dawson", "MST7"},
+    {"America/Dawson_Creek", "MST7"},
+    {"America/Denver", "MST7MDT,M3.2.0,M11.1.0"},
+    {"America/Detroit", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Dominica", "AST4"},
+    {"America/Edmonton", "CST6"},
+    {"America/Eirunepe", "<-05>5"},
+    {"America/El_Salvador", "CST6"},
+    {"America/Fort_Nelson", "MST7"},
+    {"America/Fortaleza", "<-03>3"},
+    {"America/Glace_Bay", "AST4ADT,M3.2.0,M11.1.0"},
+    {"America/Godthab", "<-02>2<-01>,M3.5.0/-1,M10.5.0/0"},
+    {"America/Goose_Bay", "AST4ADT,M3.2.0,M11.1.0"},
+    {"America/Grand_Turk", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Grenada", "AST4"},
+    {"America/Guadeloupe", "AST4"},
+    {"America/Guatemala", "CST6"},
+    {"America/Guayaquil", "<-05>5"},
+    {"America/Guyana", "<-04>4"},
+    {"America/Halifax", "AST4ADT,M3.2.0,M11.1.0"},
+    {"America/Havana", "CST5CDT,M3.2.0/0,M11.1.0/1"},
+    {"America/Hermosillo", "MST7"},
+    {"America/Indiana/Indianapolis", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Indiana/Knox", "CST6CDT,M3.2.0,M11.1.0"},
+    {"America/Indiana/Marengo", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Indiana/Petersburg", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Indiana/Tell_City", "CST6CDT,M3.2.0,M11.1.0"},
+    {"America/Indiana/Vevay", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Indiana/Vincennes", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Indiana/Winamac", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Inuvik", "CST6"},
+    {"America/Iqaluit", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Jamaica", "EST5"},
+    {"America/Juneau", "AKST9AKDT,M3.2.0,M11.1.0"},
+    {"America/Kentucky/Louisville", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Kentucky/Monticello", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Kralendijk", "AST4"},
+    {"America/La_Paz", "<-04>4"},
+    {"America/Lima", "<-05>5"},
+    {"America/Los_Angeles", "PST8PDT,M3.2.0,M11.1.0"},
+    {"America/Lower_Princes", "AST4"},
+    {"America/Maceio", "<-03>3"},
+    {"America/Managua", "CST6"},
+    {"America/Manaus", "<-04>4"},
+    {"America/Marigot", "AST4"},
+    {"America/Martinique", "AST4"},
+    {"America/Matamoros", "CST6CDT,M3.2.0,M11.1.0"},
+    {"America/Mazatlan", "MST7"},
+    {"America/Menominee", "CST6CDT,M3.2.0,M11.1.0"},
+    {"America/Merida", "CST6"},
+    {"America/Metlakatla", "AKST9AKDT,M3.2.0,M11.1.0"},
+    {"America/Mexico_City", "CST6"},
+    {"America/Miquelon", "<-03>3<-02>,M3.2.0,M11.1.0"},
+    {"America/Moncton", "AST4ADT,M3.2.0,M11.1.0"},
+    {"America/Monterrey", "CST6"},
+    {"America/Montevideo", "<-03>3"},
+    {"America/Montreal", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Montserrat", "AST4"},
+    {"America/Nassau", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/New_York", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Nipigon", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Nome", "AKST9AKDT,M3.2.0,M11.1.0"},
+    {"America/Noronha", "<-02>2"},
+    {"America/North_Dakota/Beulah", "CST6CDT,M3.2.0,M11.1.0"},
+    {"America/North_Dakota/Center", "CST6CDT,M3.2.0,M11.1.0"},
+    {"America/North_Dakota/New_Salem", "CST6CDT,M3.2.0,M11.1.0"},
+    {"America/Ojinaga", "CST6CDT,M3.2.0,M11.1.0"},
+    {"America/Panama", "EST5"},
+    {"America/Pangnirtung", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Paramaribo", "<-03>3"},
+    {"America/Phoenix", "MST7"},
+    {"America/Port-au-Prince", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Port_of_Spain", "AST4"},
+    {"America/Porto_Velho", "<-04>4"},
+    {"America/Puerto_Rico", "AST4"},
+    {"America/Punta_Arenas", "<-03>3"},
+    {"America/Rainy_River", "EST5"},
+    {"America/Rankin_Inlet", "CST6CDT,M3.2.0,M11.1.0"},
+    {"America/Recife", "<-03>3"},
+    {"America/Regina", "CST6"},
+    {"America/Resolute", "CST6CDT,M3.2.0,M11.1.0"},
+    {"America/Rio_Branco", "<-05>5"},
+    {"America/Santarem", "<-03>3"},
+    {"America/Santiago", "<-04>4<-03>,M9.1.6/24,M4.1.6/24"},
+    {"America/Santo_Domingo", "AST4"},
+    {"America/Sao_Paulo", "<-03>3"},
+    {"America/Scoresbysund", "<-02>2<-01>,M3.5.0/-1,M10.5.0/0"},
+    {"America/Sitka", "AKST9AKDT,M3.2.0,M11.1.0"},
+    {"America/St_Barthelemy", "AST4"},
+    {"America/St_Johns", "NST3:30NDT,M3.2.0,M11.1.0"},
+    {"America/St_Kitts", "AST4"},
+    {"America/St_Lucia", "AST4"},
+    {"America/St_Thomas", "AST4"},
+    {"America/St_Vincent", "AST4"},
+    {"America/Swift_Current", "CST6"},
+    {"America/Tegucigalpa", "CST6"},
+    {"America/Thule", "AST4ADT,M3.2.0,M11.1.0"},
+    {"America/Thunder_Bay", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Tijuana", "PST8PDT,M3.2.0,M11.1.0"},
+    {"America/Toronto", "EST5EDT,M3.2.0,M11.1.0"},
+    {"America/Tortola", "AST4"},
+    {"America/Vancouver", "MST7"},
+    {"America/Whitehorse", "MST7"},
+    {"America/Winnipeg", "EST5"},
+    {"America/Yakutat", "AKST9AKDT,M3.2.0,M11.1.0"},
+    {"America/Yellowknife", "CST6"},
+    {"Antarctica/Casey", "<+08>-8"},
+    {"Antarctica/Davis", "<+07>-7"},
+    {"Antarctica/DumontDUrville", "<+10>-10"},
+    {"Antarctica/Macquarie", "AEST-10AEDT,M10.1.0,M4.1.0/3"},
+    {"Antarctica/Mawson", "<+05>-5"},
+    {"Antarctica/McMurdo", "NZST-12NZDT,M9.5.0,M4.1.0/3"},
+    {"Antarctica/Palmer", "<-03>3"},
+    {"Antarctica/Rothera", "<-03>3"},
+    {"Antarctica/Syowa", "<+03>-3"},
+    {"Antarctica/Troll", "<+00>0<+02>-2,M3.5.0/1,M10.5.0/3"},
+    {"Antarctica/Vostok", "<+05>-5"},
+    {"Arctic/Longyearbyen", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Asia/Aden", "<+03>-3"},
+    {"Asia/Almaty", "<+05>-5"},
+    {"Asia/Amman", "<+03>-3"},
+    {"Asia/Anadyr", "<+12>-12"},
+    {"Asia/Aqtau", "<+05>-5"},
+    {"Asia/Aqtobe", "<+05>-5"},
+    {"Asia/Ashgabat", "<+05>-5"},
+    {"Asia/Atyrau", "<+05>-5"},
+    {"Asia/Baghdad", "<+03>-3"},
+    {"Asia/Bahrain", "<+03>-3"},
+    {"Asia/Baku", "<+04>-4"},
+    {"Asia/Bangkok", "<+07>-7"},
+    {"Asia/Barnaul", "<+07>-7"},
+    {"Asia/Beirut", "EET-2EEST,M3.5.0/0,M10.5.0/0"},
+    {"Asia/Bishkek", "<+06>-6"},
+    {"Asia/Brunei", "<+08>-8"},
+    {"Asia/Chita", "<+09>-9"},
+    {"Asia/Choibalsan", "<+08>-8"},
+    {"Asia/Colombo", "<+0530>-5:30"},
+    {"Asia/Damascus", "<+03>-3"},
+    {"Asia/Dhaka", "<+06>-6"},
+    {"Asia/Dili", "<+09>-9"},
+    {"Asia/Dubai", "<+04>-4"},
+    {"Asia/Dushanbe", "<+05>-5"},
+    {"Asia/Famagusta", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Asia/Gaza", "EET-2EEST,M3.4.4/50,M10.4.4/50"},
+    {"Asia/Hebron", "EET-2EEST,M3.4.4/50,M10.4.4/50"},
+    {"Asia/Ho_Chi_Minh", "<+07>-7"},
+    {"Asia/Hong_Kong", "HKT-8"},
+    {"Asia/Hovd", "<+07>-7"},
+    {"Asia/Irkutsk", "<+08>-8"},
+    {"Asia/Jakarta", "WIB-7"},
+    {"Asia/Jayapura", "WIT-9"},
+    {"Asia/Jerusalem", "IST-2IDT,M3.4.4/26,M10.5.0"},
+    {"Asia/Kabul", "<+0430>-4:30"},
+    {"Asia/Kamchatka", "<+12>-12"},
+    {"Asia/Karachi", "PKT-5"},
+    {"Asia/Kathmandu", "<+0545>-5:45"},
+    {"Asia/Khandyga", "<+09>-9"},
+    {"Asia/Kolkata", "IST-5:30"},
+    {"Asia/Krasnoyarsk", "<+07>-7"},
+    {"Asia/Kuala_Lumpur", "<+08>-8"},
+    {"Asia/Kuching", "<+08>-8"},
+    {"Asia/Kuwait", "<+03>-3"},
+    {"Asia/Macau", "CST-8"},
+    {"Asia/Magadan", "<+11>-11"},
+    {"Asia/Makassar", "WITA-8"},
+    {"Asia/Manila", "PST-8"},
+    {"Asia/Muscat", "<+04>-4"},
+    {"Asia/Nicosia", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Asia/Novokuznetsk", "<+07>-7"},
+    {"Asia/Novosibirsk", "<+07>-7"},
+    {"Asia/Omsk", "<+06>-6"},
+    {"Asia/Oral", "<+05>-5"},
+    {"Asia/Phnom_Penh", "<+07>-7"},
+    {"Asia/Pontianak", "WIB-7"},
+    {"Asia/Pyongyang", "KST-9"},
+    {"Asia/Qatar", "<+03>-3"},
+    {"Asia/Qyzylorda", "<+05>-5"},
+    {"Asia/Riyadh", "<+03>-3"},
+    {"Asia/Sakhalin", "<+11>-11"},
+    {"Asia/Samarkand", "<+05>-5"},
+    {"Asia/Seoul", "KST-9"},
+    {"Asia/Shanghai", "CST-8"},
+    {"Asia/Singapore", "<+08>-8"},
+    {"Asia/Srednekolymsk", "<+11>-11"},
+    {"Asia/Taipei", "CST-8"},
+    {"Asia/Tashkent", "<+05>-5"},
+    {"Asia/Tbilisi", "<+04>-4"},
+    {"Asia/Tehran", "<+0330>-3:30"},
+    {"Asia/Thimphu", "<+06>-6"},
+    {"Asia/Tokyo", "JST-9"},
+    {"Asia/Tomsk", "<+07>-7"},
+    {"Asia/Ulaanbaatar", "<+08>-8"},
+    {"Asia/Urumqi", "<+06>-6"},
+    {"Asia/Ust-Nera", "<+10>-10"},
+    {"Asia/Vientiane", "<+07>-7"},
+    {"Asia/Vladivostok", "<+10>-10"},
+    {"Asia/Yakutsk", "<+09>-9"},
+    {"Asia/Yangon", "<+0630>-6:30"},
+    {"Asia/Yekaterinburg", "<+05>-5"},
+    {"Asia/Yerevan", "<+04>-4"},
+    {"Atlantic/Azores", "<-01>1<+00>,M3.5.0/0,M10.5.0/1"},
+    {"Atlantic/Bermuda", "AST4ADT,M3.2.0,M11.1.0"},
+    {"Atlantic/Canary", "WET0WEST,M3.5.0/1,M10.5.0"},
+    {"Atlantic/Cape_Verde", "<-01>1"},
+    {"Atlantic/Faroe", "WET0WEST,M3.5.0/1,M10.5.0"},
+    {"Atlantic/Madeira", "WET0WEST,M3.5.0/1,M10.5.0"},
+    {"Atlantic/Reykjavik", "GMT0"},
+    {"Atlantic/South_Georgia", "<-02>2"},
+    {"Atlantic/St_Helena", "GMT0"},
+    {"Atlantic/Stanley", "<-03>3"},
+    {"Australia/Adelaide", "ACST-9:30ACDT,M10.1.0,M4.1.0/3"},
+    {"Australia/Brisbane", "AEST-10"},
+    {"Australia/Broken_Hill", "ACST-9:30ACDT,M10.1.0,M4.1.0/3"},
+    {"Australia/Currie", "AEST-10AEDT,M10.1.0,M4.1.0/3"},
+    {"Australia/Darwin", "ACST-9:30"},
+    {"Australia/Eucla", "<+0845>-8:45"},
+    {"Australia/Hobart", "AEST-10AEDT,M10.1.0,M4.1.0/3"},
+    {"Australia/Lindeman", "AEST-10"},
+    {"Australia/Lord_Howe", "<+1030>-10:30<+11>-11,M10.1.0,M4.1.0"},
+    {"Australia/Melbourne", "AEST-10AEDT,M10.1.0,M4.1.0/3"},
+    {"Australia/Perth", "AWST-8"},
+    {"Australia/Sydney", "AEST-10AEDT,M10.1.0,M4.1.0/3"},
+    {"Etc/GMT", "GMT0"},
+    {"Etc/GMT+0", "GMT0"},
+    {"Etc/GMT+1", "<-01>1"},
+    {"Etc/GMT+10", "<-10>10"},
+    {"Etc/GMT+11", "<-11>11"},
+    {"Etc/GMT+12", "<-12>12"},
+    {"Etc/GMT+2", "<-02>2"},
+    {"Etc/GMT+3", "<-03>3"},
+    {"Etc/GMT+4", "<-04>4"},
+    {"Etc/GMT+5", "<-05>5"},
+    {"Etc/GMT+6", "<-06>6"},
+    {"Etc/GMT+7", "<-07>7"},
+    {"Etc/GMT+8", "<-08>8"},
+    {"Etc/GMT+9", "<-09>9"},
+    {"Etc/GMT-0", "GMT0"},
+    {"Etc/GMT-1", "<+01>-1"},
+    {"Etc/GMT-10", "<+10>-10"},
+    {"Etc/GMT-11", "<+11>-11"},
+    {"Etc/GMT-12", "<+12>-12"},
+    {"Etc/GMT-13", "<+13>-13"},
+    {"Etc/GMT-14", "<+14>-14"},
+    {"Etc/GMT-2", "<+02>-2"},
+    {"Etc/GMT-3", "<+03>-3"},
+    {"Etc/GMT-4", "<+04>-4"},
+    {"Etc/GMT-5", "<+05>-5"},
+    {"Etc/GMT-6", "<+06>-6"},
+    {"Etc/GMT-7", "<+07>-7"},
+    {"Etc/GMT-8", "<+08>-8"},
+    {"Etc/GMT-9", "<+09>-9"},
+    {"Etc/GMT0", "GMT0"},
+    {"Etc/Greenwich", "GMT0"},
+    {"Etc/UCT", "UTC0"},
+    {"Etc/UTC", "UTC0"},
+    {"Etc/Universal", "UTC0"},
+    {"Etc/Zulu", "UTC0"},
+    {"Europe/Amsterdam", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Andorra", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Astrakhan", "<+04>-4"},
+    {"Europe/Athens", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Belgrade", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Berlin", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Bratislava", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Brussels", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Bucharest", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Budapest", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Busingen", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Chisinau", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Copenhagen", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Dublin", "IST-1GMT0,M10.5.0,M3.5.0/1"},
+    {"Europe/Gibraltar", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Guernsey", "GMT0BST,M3.5.0/1,M10.5.0"},
+    {"Europe/Helsinki", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Isle_of_Man", "GMT0BST,M3.5.0/1,M10.5.0"},
+    {"Europe/Istanbul", "<+03>-3"},
+    {"Europe/Jersey", "GMT0BST,M3.5.0/1,M10.5.0"},
+    {"Europe/Kaliningrad", "EET-2"},
+    {"Europe/Kiev", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Kirov", "MSK-3"},
+    {"Europe/Lisbon", "WET0WEST,M3.5.0/1,M10.5.0"},
+    {"Europe/Ljubljana", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/London", "GMT0BST,M3.5.0/1,M10.5.0"},
+    {"Europe/Luxembourg", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Madrid", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Malta", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Mariehamn", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Minsk", "<+03>-3"},
+    {"Europe/Monaco", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Moscow", "MSK-3"},
+    {"Europe/Oslo", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Paris", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Podgorica", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Prague", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Riga", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Rome", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Samara", "<+04>-4"},
+    {"Europe/San_Marino", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Sarajevo", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Saratov", "<+04>-4"},
+    {"Europe/Simferopol", "MSK-3"},
+    {"Europe/Skopje", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Sofia", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Stockholm", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Tallinn", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Tirane", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Ulyanovsk", "<+04>-4"},
+    {"Europe/Uzhgorod", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Vaduz", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Vatican", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Vienna", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Vilnius", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Volgograd", "MSK-3"},
+    {"Europe/Warsaw", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Zagreb", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Europe/Zaporozhye", "EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"Europe/Zurich", "CET-1CEST,M3.5.0,M10.5.0/3"},
+    {"Indian/Antananarivo", "EAT-3"},
+    {"Indian/Chagos", "<+06>-6"},
+    {"Indian/Christmas", "<+07>-7"},
+    {"Indian/Cocos", "<+0630>-6:30"},
+    {"Indian/Comoro", "EAT-3"},
+    {"Indian/Kerguelen", "<+05>-5"},
+    {"Indian/Mahe", "<+04>-4"},
+    {"Indian/Maldives", "<+05>-5"},
+    {"Indian/Mauritius", "<+04>-4"},
+    {"Indian/Mayotte", "EAT-3"},
+    {"Indian/Reunion", "<+04>-4"},
+    {"Pacific/Apia", "<+13>-13"},
+    {"Pacific/Auckland", "NZST-12NZDT,M9.5.0,M4.1.0/3"},
+    {"Pacific/Bougainville", "<+11>-11"},
+    {"Pacific/Chatham", "<+1245>-12:45<+1345>,M9.5.0/2:45,M4.1.0/3:45"},
+    {"Pacific/Chuuk", "<+10>-10"},
+    {"Pacific/Easter", "<-06>6<-05>,M9.1.6/22,M4.1.6/22"},
+    {"Pacific/Efate", "<+11>-11"},
+    {"Pacific/Enderbury", "<+13>-13"},
+    {"Pacific/Fakaofo", "<+13>-13"},
+    {"Pacific/Fiji", "<+12>-12"},
+    {"Pacific/Funafuti", "<+12>-12"},
+    {"Pacific/Galapagos", "<-06>6"},
+    {"Pacific/Gambier", "<-09>9"},
+    {"Pacific/Guadalcanal", "<+11>-11"},
+    {"Pacific/Guam", "ChST-10"},
+    {"Pacific/Honolulu", "HST10"},
+    {"Pacific/Kiritimati", "<+14>-14"},
+    {"Pacific/Kosrae", "<+11>-11"},
+    {"Pacific/Kwajalein", "<+12>-12"},
+    {"Pacific/Majuro", "<+12>-12"},
+    {"Pacific/Marquesas", "<-0930>9:30"},
+    {"Pacific/Midway", "SST11"},
+    {"Pacific/Nauru", "<+12>-12"},
+    {"Pacific/Niue", "<-11>11"},
+    {"Pacific/Norfolk", "<+11>-11<+12>,M10.1.0,M4.1.0/3"},
+    {"Pacific/Noumea", "<+11>-11"},
+    {"Pacific/Pago_Pago", "SST11"},
+    {"Pacific/Palau", "<+09>-9"},
+    {"Pacific/Pitcairn", "<-08>8"},
+    {"Pacific/Pohnpei", "<+11>-11"},
+    {"Pacific/Port_Moresby", "<+10>-10"},
+    {"Pacific/Rarotonga", "<-10>10"},
+    {"Pacific/Saipan", "ChST-10"},
+    {"Pacific/Tahiti", "<-10>10"},
+    {"Pacific/Tarawa", "<+12>-12"},
+    {"Pacific/Tongatapu", "<+13>-13"},
+    {"Pacific/Wake", "<+12>-12"},
+    {"Pacific/Wallis", "<+12>-12"},
+};
+
+inline int emsesp_tz_zone_cmp(const void * key, const void * element) {
+    return strcmp(static_cast<const char *>(key), static_cast<const EmsespTzZone *>(element)->label);
+}
+
+// Returns the POSIX TZ string for an IANA label, or nullptr if unknown.
+inline const char * emsesp_tz_format_for_label(const char * label) {
+    if (label == nullptr || *label == '\0') {
+        return nullptr;
+    }
+    const auto * found = static_cast<const EmsespTzZone *>(
+        bsearch(label, EMSESP_TZ_ZONES, EMSESP_TZ_ZONE_COUNT, sizeof(EmsespTzZone), emsesp_tz_zone_cmp));
+    return found != nullptr ? found->format : nullptr;
+}