Adding timezone support

lib/I18n/translations/english.yaml

@@ -85,12 +85,36 @@ STR_SHOW_HIDDEN_FILES: "Show Hidden Files"
 STR_KEEP_CLOCK_ALIVE: "Keep Clock Alive"
 STR_CLOCK: "Clock"
 STR_CLOCK_FORMAT: "Clock Format"
+STR_TIMEZONE: "Timezone"
 STR_24H: "24h"
 STR_12H: "12h"
+STR_TZ_UTC: "UTC (GMT/BST)"
+STR_TZ_CET: "Central Europe (CET/CEST)"
+STR_TZ_EET: "Eastern Europe (EET/EEST)"
+STR_TZ_EST: "US Eastern (EST/EDT)"
+STR_TZ_CST: "US Central (CST/CDT)"
+STR_TZ_MST: "US Mountain (MST/MDT)"
+STR_TZ_PST: "US Pacific (PST/PDT)"
+STR_TZ_AEST: "Australia Eastern (AEST/AEDT)"
+STR_TZ_NZST: "New Zealand (NZST/NZDT)"
+STR_TZ_MSK: "Russia (MSK)"
+STR_TZ_UTC_MINUS3: "South America (UTC-3)"
+STR_TZ_UTC_PLUS4: "Gulf (UTC+4)"
+STR_TZ_IST: "India (UTC+5:30)"
+STR_TZ_UTC_PLUS7: "SE Asia (UTC+7)"
+STR_TZ_UTC_PLUS8: "China/SE Asia (UTC+8)"
+STR_TZ_UTC_PLUS9: "Japan/Korea (UTC+9)"
 STR_SYNC_TIME: "Sync Time"
+STR_DETECT_TIMEZONE: "Detect Timezone"
 STR_SYNCING_CLOCK: "Syncing clock..."
+STR_DETECTING_TIMEZONE: "Detecting timezone..."
 STR_TIME_SYNCED: "Time synced"
 STR_TIME_SYNC_FAILED: "Time sync failed"
+STR_TIMEZONE_DETECTED: "Timezone detected"
+STR_TIMEZONE_DETECT_FAILED: "Timezone detect failed"
+STR_DST_ACTIVE: "DST: active"
+STR_DST_INACTIVE: "DST: inactive"
+STR_DST_UNKNOWN: "DST: unknown"
 STR_REFRESH_FREQ: "Refresh Frequency"
 STR_KOREADER_SYNC: "KOReader Sync"
 STR_CHECK_UPDATES: "Check for updates"

lib/hal/HalClock.cpp

@@ -6,6 +6,9 @@
 #include <esp_private/esp_clk.h>
 #include <esp_sntp.h>
 #include <sys/time.h>
+#include <time.h>
+
+#include <cstdlib>
 
 // ---- RTC-memory state (survives deep sleep, not cold boot) ----------------
 
@@ -19,6 +22,29 @@ RTC_NOINIT_ATTR static uint64_t rtcLpTimeUs;  // esp_clk_rtc_time() at capture
 
 static bool clockApproximate = true;
 
+struct TimeZoneEntry {
+  const char* tz;
+};
+
+static constexpr TimeZoneEntry TIMEZONES[] = {
+    {"GMT0BST,M3.5.0/1,M10.5.0/2"},
+    {"CET-1CEST,M3.5.0/2,M10.5.0/3"},
+    {"EET-2EEST,M3.5.0/3,M10.5.0/4"},
+    {"MSK-3"},
+    {"UTC-4"},
+    {"UTC-5:30"},
+    {"UTC-7"},
+    {"UTC-8"},
+    {"UTC-9"},
+    {"AEST-10AEDT,M10.1.0/2,M4.1.0/3"},
+    {"NZST-12NZDT,M9.5.0/2,M4.1.0/3"},
+    {"UTC+3"},
+    {"EST5EDT,M3.2.0/2,M11.1.0/2"},
+    {"CST6CDT,M3.2.0/2,M11.1.0/2"},
+    {"MST7MDT,M3.2.0/2,M11.1.0/2"},
+    {"PST8PDT,M3.2.0/2,M11.1.0/2"},
+};
+
 // ---- NVS helpers ----------------------------------------------------------
 
 static constexpr char NVS_NAMESPACE[] = "halclock";
@@ -65,6 +91,13 @@ static void capture(bool lpValid) {
 
 namespace HalClock {
 
+void applyTimezone(uint8_t timeZoneSetting) {
+  const size_t index = timeZoneSetting < (sizeof(TIMEZONES) / sizeof(TIMEZONES[0])) ? timeZoneSetting : 0;
+  setenv("TZ", TIMEZONES[index].tz, 1);
+  tzset();
+  LOG_DBG("CLK", "Timezone applied: %s", TIMEZONES[index].tz);
+}
+
 bool syncNtp() {
   if (esp_sntp_enabled()) {
     esp_sntp_stop();

lib/hal/HalClock.h

@@ -30,6 +30,9 @@ namespace HalClock {
 /// Returns true if the sync succeeded.
 bool syncNtp();
 
+/// Apply timezone/DST rules via the POSIX TZ string for the given setting.
+void applyTimezone(uint8_t timeZoneSetting);
+
 /// Call just before deep sleep.  Snapshots the current system time to RTC
 /// memory and NVS so it can be restored on wake / cold boot.  Pass true when
 /// the LP timer is kept alive during sleep.