diff --git a/sonoff/_changelog.ino b/sonoff/_changelog.ino
index edd41da27..9c1c9d92b 100644
--- a/sonoff/_changelog.ino
+++ b/sonoff/_changelog.ino
@@ -1,6 +1,7 @@
 /*********************************************************************************************\
  * 6.6.0.4 20190806
  * Add support for CHIRP soil moisture sensor by Christian Baars
+ * Add debug compile features using defines DEBUG_TASMOTA_DRIVER and DEBUG_TASMOTA_SENSOR. See example in xdrv_09_timers.ino
  *
  * 6.6.0.3 20190725
  * Change filename of configuration backup from using FriendlyName1 to Hostname solving diacritic issues (#2422)
diff --git a/sonoff/my_user_config.h b/sonoff/my_user_config.h
index 589068166..9a1fadb44 100644
--- a/sonoff/my_user_config.h
+++ b/sonoff/my_user_config.h
@@ -493,9 +493,11 @@
 //#define USE_HRE                                  // Add support for Badger HR-E Water Meter (+1k4 code)
 
 /*********************************************************************************************\
- * Debug features are only supported in development branch
+ * Debug features
 \*********************************************************************************************/
 
+//#define DEBUG_TASMOTA_DRIVER                     // Enable driver debug messages
+//#define DEBUG_TASMOTA_SENSOR                     // Enable sensor debug messages
 //#define USE_DEBUG_DRIVER                         // Use xdrv_99_debug.ino providing commands CpuChk, CfgXor, CfgDump, CfgPeek and CfgPoke
 
 /*********************************************************************************************\
diff --git a/sonoff/sonoff_post.h b/sonoff/sonoff_post.h
index 1a218311f..4eca7aafd 100644
--- a/sonoff/sonoff_post.h
+++ b/sonoff/sonoff_post.h
@@ -517,4 +517,16 @@ void KNX_CB_Action(message_t const &msg, void *arg);
 #undef USE_MQTT_TLS_CA_CERT
 #endif
 
+#ifdef DEBUG_TASMOTA_DRIVER
+#define DEBUG_DRIVER_LOG(...) AddLog_Debug(__VA_ARGS__)
+#else
+#define DEBUG_DRIVER_LOG(...)
+#endif
+
+#ifdef DEBUG_TASMOTA_SENSOR
+#define DEBUG_SENSOR_LOG(...) AddLog_Debug(__VA_ARGS__)
+#else
+#define DEBUG_SENSOR_LOG(...)
+#endif
+
 #endif  // _SONOFF_POST_H_
diff --git a/sonoff/support.ino b/sonoff/support.ino
index 1f263a466..9d7a5ef3b 100644
--- a/sonoff/support.ino
+++ b/sonoff/support.ino
@@ -1511,6 +1511,16 @@ void AddLog_P2(uint32_t loglevel, PGM_P formatP, ...)
   AddLog(loglevel);
 }
 
+void AddLog_Debug(PGM_P formatP, ...)
+{
+  va_list arg;
+  va_start(arg, formatP);
+  vsnprintf_P(log_data, sizeof(log_data), formatP, arg);
+  va_end(arg);
+
+  AddLog(LOG_LEVEL_DEBUG);
+}
+
 void AddLogBuffer(uint32_t loglevel, uint8_t *buffer, uint32_t count)
 {
   snprintf_P(log_data, sizeof(log_data), PSTR("DMP:"));
diff --git a/sonoff/xdrv_09_timers.ino b/sonoff/xdrv_09_timers.ino
index 193456df5..90a61c250 100644
--- a/sonoff/xdrv_09_timers.ino
+++ b/sonoff/xdrv_09_timers.ino
@@ -282,9 +282,14 @@ void TimerEverySecond(void)
         }
 #endif
         if (xtimer.arm) {
-          set_time += timer_window[i];                // Add random time offset
-          if (set_time < 0) { set_time = 0; }         // Stay today;
-          if (set_time > 1439) { set_time = 1439; }
+          set_time += timer_window[i];                            // Add random time offset
+          if (set_time < 0) { set_time = abs(timer_window[i]); }  // After midnight and within negative window so stay today but allow positive randomness;
+          if (set_time > 1439) { set_time = 1439; }               // Stay today
+
+          if (0 == i) {
+            DEBUG_DRIVER_LOG(PSTR("TIM: Timer 1 XTimerTime %d, Window %d, SetTime %d"), xtimer.time, timer_window[i], set_time);
+          }
+
           if (time == set_time) {
             if (xtimer.days & days) {
               Settings.timer[i].arm = xtimer.repeat;