From 92ac7e8810c946e0b8dd88f70683e813372076df Mon Sep 17 00:00:00 2001
From: acidburns <neon22@web.de>
Date: Wed, 18 Feb 2026 01:34:47 +0100
Subject: [PATCH] receiver: store CSVs by local date and keep UTC history
 fallback

---
 src/sd_logger.cpp  | 14 +++++++-------
 src/web_server.cpp | 22 ++++++++++++++++++++--
 2 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/src/sd_logger.cpp b/src/sd_logger.cpp
index f0660c5..8e1db43 100644
--- a/src/sd_logger.cpp
+++ b/src/sd_logger.cpp
@@ -27,15 +27,15 @@ static bool ensure_dir(const String &path) {
   return SD.mkdir(path);
 }
 
-static String format_date_utc(uint32_t ts_utc) {
+static String format_date_local(uint32_t ts_utc) {
   time_t t = static_cast<time_t>(ts_utc);
-  struct tm tm_utc;
-  gmtime_r(&t, &tm_utc);
+  struct tm tm_local;
+  localtime_r(&t, &tm_local);
   char buf[16];
   snprintf(buf, sizeof(buf), "%04d-%02d-%02d",
-           tm_utc.tm_year + 1900,
-           tm_utc.tm_mon + 1,
-           tm_utc.tm_mday);
+           tm_local.tm_year + 1900,
+           tm_local.tm_mon + 1,
+           tm_local.tm_mday);
   return String(buf);
 }
 
@@ -94,7 +94,7 @@ void sd_logger_log_sample(const MeterData &data, bool include_error_text) {
     return;
   }
 
-  String filename = sender_dir + "/" + format_date_utc(data.ts_utc) + ".csv";
+  String filename = sender_dir + "/" + format_date_local(data.ts_utc) + ".csv";
   bool new_file = !SD.exists(filename);
   File f = SD.open(filename, FILE_APPEND);
   if (!f) {
diff --git a/src/web_server.cpp b/src/web_server.cpp
index 40cc317..b22da72 100644
--- a/src/web_server.cpp
+++ b/src/web_server.cpp
@@ -243,7 +243,16 @@ static void history_reset() {
   g_history = {};
 }
 
-static String history_date_from_epoch(uint32_t ts_utc) {
+static String history_date_from_epoch_local(uint32_t ts_utc) {
+  time_t t = static_cast<time_t>(ts_utc);
+  struct tm tm_local;
+  localtime_r(&t, &tm_local);
+  char buf[16];
+  snprintf(buf, sizeof(buf), "%04d-%02d-%02d", tm_local.tm_year + 1900, tm_local.tm_mon + 1, tm_local.tm_mday);
+  return String(buf);
+}
+
+static String history_date_from_epoch_utc(uint32_t ts_utc) {
   time_t t = static_cast<time_t>(ts_utc);
   struct tm tm_utc;
   gmtime_r(&t, &tm_utc);
@@ -298,8 +307,17 @@ static bool history_open_next_file() {
     g_history.done = true;
     return false;
   }
-  String path = String("/dd3/") + g_history.device_id + "/" + history_date_from_epoch(day_ts) + ".csv";
+  String local_date = history_date_from_epoch_local(day_ts);
+  String path = String("/dd3/") + g_history.device_id + "/" + local_date + ".csv";
   g_history.file = SD.open(path.c_str(), FILE_READ);
+  if (!g_history.file) {
+    // Compatibility fallback for files written before local-date partitioning.
+    String utc_date = history_date_from_epoch_utc(day_ts);
+    if (utc_date != local_date) {
+      String legacy_path = String("/dd3/") + g_history.device_id + "/" + utc_date + ".csv";
+      g_history.file = SD.open(legacy_path.c_str(), FILE_READ);
+    }
+  }
   g_history.day_index++;
   return true;
 }