diff --git a/lambda/Makefile b/lambda/Makefile
index 0fb356a..69df61a 100644
--- a/lambda/Makefile
+++ b/lambda/Makefile
@@ -13,7 +13,7 @@
 MAIN = lambda.c
 
 ## en: 0 (default), de: 1
-LANG = 1
+LANG = 0
 
 ## If you've split your program into multiple .c / .h files, 
 ## include the additional source (in same directory) here 
diff --git a/lambda/display.c b/lambda/display.c
index cb9578d..b9e748a 100644
--- a/lambda/display.c
+++ b/lambda/display.c
@@ -17,12 +17,15 @@
 #include "usart.h"
 #include "lcdroutines.h"
 #include "integers.h"
+#include "interrupts.h"
 #include "display.h"
 #include "alert.h"
+#include "messages.h"
 
 #define MENU_OFF 0
 #define MENU_MAX_VALUES 1
 #define MENU_LAST_TEXT 2
+#define MENU_TIME 3
 
 uint8_t position = MENU_OFF;
 bool updatePending = false;
@@ -43,8 +46,8 @@
 }
 
 /**
- * Formats the given measurement values and displays them on an 16x2 LCD along
- * with the given hint.
+ * Formats the given measurement values and displays them along with the
+ * given hint.
  */
 static void displayMeas(Measurement const meas, char* const hint) {
 	uint16_t lambdax100 = divRoundNearest(meas.lambda, 10);
@@ -58,6 +61,20 @@
 	setText(line0, line1);
 }
 
+/**
+ * Formats and displays the time since last start/reset.
+ */
+static void displayTime(void) {
+	uint32_t time = getTime();
+	uint16_t hours = time / 3600;
+	uint8_t mins = time % 3600 / 60;
+	uint8_t secs = time % 60;
+
+	char line1[17];
+	snprintf(line1, sizeof(line1), "%u:%02u:%02u", hours, mins, secs);
+	setText(MSG_TIME_SINCE_START, line1);
+}
+
 void cycleDisplay(void) {
 	if (isAlertActive()) {
 		// button pressed during alert
@@ -66,12 +83,10 @@
 		return;
 	}
 	position++;
-	if (position > MENU_LAST_TEXT) {
+	if (position > MENU_TIME) {
 		position = MENU_OFF;
 	}
-	if (position == MENU_LAST_TEXT) {
-		lcd_clear();
-	}
+	lcd_clear();
 	updatePending = true;
 	beep(1, 2, 31);
 }
@@ -102,6 +117,8 @@
 			displayMeas(measMax, "|>");
 		} else if (position == MENU_LAST_TEXT) {
 			setText(lastLine0, lastLine1);
+		} else if (position == MENU_TIME) {
+			displayTime();
 		} else {
 			displayMeas(measLatest, "  ");
 		}
diff --git a/lambda/interrupts.c b/lambda/interrupts.c
index 454389a..6e325b8 100644
--- a/lambda/interrupts.c
+++ b/lambda/interrupts.c
@@ -19,13 +19,13 @@
 #include "alert.h"
 
 static volatile bool buttonPressed = false;
-static volatile uint32_t time = 0;
+static volatile uint32_t ints = 0;
 
 /**
  * Called about every 16.4 ms.
  */
 ISR(TIMER0_OVF_vect) {
-	time++;
+	ints++;
 	oscillateBeep();
 	if (bit_is_clear(PINB, PB0) && ! buttonPressed) {
 		buttonPressed = true;
@@ -35,17 +35,21 @@
 	}
 }
 
-uint32_t getTime(void) {
-	uint32_t atomicTime;
+uint32_t getInts(void) {
+	uint32_t atomicInts;
 	ATOMIC_BLOCK(ATOMIC_FORCEON) {
-		atomicTime = time;
+		atomicInts = ints;
 	}
-	return atomicTime;
+	return atomicInts;
+}
+
+uint32_t getTime(void) {
+	return getInts() / INTS_PER_SEC;
 }
 
 void resetTime(void) {
 	ATOMIC_BLOCK(ATOMIC_FORCEON) {
-		time = 0;
+		ints = 0;
 	}
 }
 
diff --git a/lambda/interrupts.h b/lambda/interrupts.h
index 37ebcd6..343a8e1 100644
--- a/lambda/interrupts.h
+++ b/lambda/interrupts.h
@@ -11,10 +11,17 @@
 #ifndef INTERRUPTS_H_
 #define INTERRUPTS_H_
 
-#define SECOND 61
+// 61 +/-1 depending on internal oscillator?
+#define INTS_PER_SEC 61
 
 /**
- * Returns the time in units of about 16.4 ms since last reset.
+ * Returns the count of interrupts occurring about every 16.4 ms
+ * since last reset.
+ */
+uint32_t getInts(void);
+
+/**
+ * Returns the time in about seconds since last reset.
  */
 uint32_t getTime(void);
 
diff --git a/lambda/lambda.c b/lambda/lambda.c
index 6c088e1..b9bb9af 100644
--- a/lambda/lambda.c
+++ b/lambda/lambda.c
@@ -52,12 +52,14 @@
 	// spend some time on being polite
 	_delay_ms(3000);
 	setHeatingOn(true);
+	_delay_ms(1000);
 
 	Measurement meas;
 
 	// main loop
 	while (true) {
-		if (getTime() % SECOND == 0 && ! isSimulation() &&
+		// TODO use getTime() here as well and get rid of getInts()?
+		if (getInts() % INTS_PER_SEC == 0 && ! isSimulation() &&
 				getHeatingState() != HEATING_FAULT) {
 			meas = measure();
 			if (isLogging()) {
diff --git a/lambda/messages.h b/lambda/messages.h
index 2b90403..c5c7810 100644
--- a/lambda/messages.h
+++ b/lambda/messages.h
@@ -36,6 +36,7 @@
 	#define MSG_HEATING_READY_1 "ready"
 	#define MSG_HEATING_FAULT_0 "Oxygen sensor"
 	#define MSG_HEATING_FAULT_1 "heating fault!"
+	#define MSG_TIME_SINCE_START "Time since start"
 
 #elif LANG == 1
 
@@ -61,6 +62,7 @@
 	#define MSG_HEATING_READY_1 "bereit"
 	#define MSG_HEATING_FAULT_0 "Lambdasonden-"
 	#define MSG_HEATING_FAULT_1 "heizung Fehler!"
+	#define MSG_TIME_SINCE_START "Zeit seit Start"
 
 #endif
 
diff --git a/lambda/rules.c b/lambda/rules.c
index a370e14..86cd15b 100644
--- a/lambda/rules.c
+++ b/lambda/rules.c
@@ -121,7 +121,7 @@
 		return;
 	}
 	if (meas.current > HEATING_SHORT_MA || meas.current < HEATING_DISCONN_MA ||
-			(getTime() > SECOND * 120 && meas.current > HEATING_READY_MA)) {
+			(getTime() > 120 && meas.current > HEATING_READY_MA)) {
 		// short circuit or disconnected or did not warm up within 2 minutes
 		setHeatingOn(false);
 		setHeatingState(HEATING_FAULT);
@@ -136,7 +136,7 @@
  */
 static void heatingTimeout(bool* const fired, int8_t const dir,
 		Measurement const meas) {
-	if (isHeatingOn() && getTime() > SECOND * 10800UL && meas.tempI < 400) {
+	if (isHeatingOn() && getTime() > 10800 && meas.tempI < 400) {
 		setHeatingOn(false);
 	}
 }