[api] Fix clock conflicts when multiple clients connected to homeassistant time (#13253)

esphome/components/api/api_server.cpp

@@ -558,8 +558,10 @@ bool APIServer::clear_noise_psk(bool make_active) {
 #ifdef USE_HOMEASSISTANT_TIME
 void APIServer::request_time() {
   for (auto &client : this->clients_) {
-    if (!client->flags_.remove && client->is_authenticated())
+    if (!client->flags_.remove && client->is_authenticated()) {
       client->send_time_request();
+      return;  // Only request from one client to avoid clock conflicts
+    }
   }
 }
 #endif

esphome/components/time/real_time_clock.cpp

@@ -31,6 +31,18 @@ void RealTimeClock::dump_config() {
 
 void RealTimeClock::synchronize_epoch_(uint32_t epoch) {
   ESP_LOGVV(TAG, "Got epoch %" PRIu32, epoch);
+  // Skip if time is already synchronized to avoid unnecessary writes, log spam,
+  // and prevent clock jumping backwards due to network latency
+  constexpr time_t min_valid_epoch = 1546300800;  // January 1, 2019
+  time_t current_time = this->timestamp_now();
+  // Check if time is valid (year >= 2019) before comparing
+  if (current_time >= min_valid_epoch) {
+    // Unsigned subtraction handles wraparound correctly, then cast to signed
+    int32_t diff = static_cast<int32_t>(epoch - static_cast<uint32_t>(current_time));
+    if (diff >= -1 && diff <= 1) {
+      return;
+    }
+  }
   // Update UTC epoch time.
 #ifdef USE_ZEPHYR
   struct timespec ts;