diff --git a/include/cyclic.h b/include/cyclic.h
index 10509f1b..6bd9b2a7 100644
--- a/include/cyclic.h
+++ b/include/cyclic.h
@@ -15,7 +15,6 @@ extern Ticker cyclicTimer;
 
 void setCyclicIRQ(void);
 void doHousekeeping(void);
-uint64_t _uptime(uint64_t diff);
 uint64_t uptime(void);
 void reset_counters(void);
 uint32_t getFreeRAM();
diff --git a/include/reset.h b/include/reset.h
index 69735a77..f540ff62 100644
--- a/include/reset.h
+++ b/include/reset.h
@@ -13,4 +13,6 @@ void do_reset(bool warmstart);
 void do_after_reset(void);
 void enter_deepsleep(const uint64_t wakeup_sec, const gpio_num_t wakeup_gpio);
 
+extern RTC_DATA_ATTR unsigned long RTC_millis;
+
 #endif // _RESET_H
\ No newline at end of file
diff --git a/src/cyclic.cpp b/src/cyclic.cpp
index 7e12db65..b6dd1120 100644
--- a/src/cyclic.cpp
+++ b/src/cyclic.cpp
@@ -20,8 +20,6 @@ void setCyclicIRQ() {
 // do all housekeeping
 void doHousekeeping() {
 
-  // update uptime counter
-  uptime();
   // check if update mode trigger switch was set
   if (RTC_runmode == RUNMODE_UPDATE) {
     // check battery status if we can before doing ota
@@ -136,13 +134,7 @@ void doHousekeeping() {
 
 } // doHousekeeping()
 
-uint64_t _uptime(uint64_t diff) {
-  static uint64_t offset = 0;
-  offset += diff;
-  return millis() + offset;
-}
-
-uint64_t uptime(void){return _uptime(0);};
+uint64_t uptime() { return (RTC_millis + millis()); }
 
 uint32_t getFreeRAM() {
 #ifndef BOARD_HAS_PSRAM
diff --git a/src/reset.cpp b/src/reset.cpp
index 40fd9772..ade00195 100644
--- a/src/reset.cpp
+++ b/src/reset.cpp
@@ -11,6 +11,7 @@ static const char TAG[] = __FILE__;
 // variables keep its values after a wakeup from sleep
 RTC_DATA_ATTR runmode_t RTC_runmode = RUNMODE_POWERCYCLE;
 RTC_DATA_ATTR struct timeval RTC_sleep_start_time;
+RTC_DATA_ATTR unsigned long RTC_millis = 0;
 timeval sleep_stop_time;
 
 const char *runmode[5] = {"powercycle", "normal", "wakeup", "update", "sleep"};
@@ -49,7 +50,7 @@ void do_after_reset(void) {
         (sleep_stop_time.tv_sec - RTC_sleep_start_time.tv_sec) * 1000 +
         (sleep_stop_time.tv_usec - RTC_sleep_start_time.tv_usec) / 1000;
     ESP_LOGI(TAG, "Time spent in deep sleep: %d ms", sleep_time_ms);
-    _uptime(sleep_time_ms); // increment uptime
+    RTC_millis += sleep_time_ms; // increment system monotonic time
 
     RTC_runmode = RUNMODE_WAKEUP;
     break;
@@ -180,8 +181,9 @@ void enter_deepsleep(const uint64_t wakeup_sec = 60,
     esp_sleep_enable_ext1_wakeup(1ULL << wakeup_gpio, ESP_EXT1_WAKEUP_ALL_LOW);
   }
 
-  // time stamp sleep start time. Deep sleep.
+  // time stamp sleep start time and save system monotonic time. Deep sleep.
   gettimeofday(&RTC_sleep_start_time, NULL);
+  RTC_millis = millis();
   ESP_LOGI(TAG, "Going to sleep, good bye.");
   esp_deep_sleep_start();