diff --git a/README.md b/README.md
index 871c868..b0cf77d 100644
--- a/README.md
+++ b/README.md
@@ -3,23 +3,23 @@ Arduino library to support STM32 Low Power.
 
 ## Requirement
  * [Arduino_Core_STM32](https://github.com/stm32duino/Arduino_Core_STM32) version >= 1.3.0
- * [STM32RTC](https://github.com/stm32duino/STM32RTC)
+ * [STM32RTC](https://github.com/stm32duino/STM32RTC) version >= 1.0.4
 
 ## API
 
 * **`void begin()`**: configure the Low Power
 
 * **`void idle(uint32_t millis)`**: enter in idle mode  
-**param** millis (optional): number of milliseconds before to exit the mode. At least 1000 ms. The RTC is used in alarm mode to wakeup the chip in millis milliseconds.
+**param** millis (optional): number of milliseconds before to exit the mode. The RTC is used in alarm mode to wakeup the chip in millis milliseconds.
 
 * **`void sleep(uint32_t millis)`**: enter in sleep mode  
-**param** millis (optional): number of milliseconds before to exit the mode. At least 1000 ms. The RTC is used in alarm mode to wakeup the chip in millis milliseconds.
+**param** millis (optional): number of milliseconds before to exit the mode. he RTC is used in alarm mode to wakeup the chip in millis milliseconds.
 
 * **`void deepSleep(uint32_t millis)`**: enter in deepSleep mode  
-**param** millis (optional): number of milliseconds before to exit the mode. At least 1000 ms. The RTC is used in alarm mode to wakeup the chip in millis milliseconds.
+**param** millis (optional): number of milliseconds before to exit the mode. The RTC is used in alarm mode to wakeup the chip in millis milliseconds.
 
 * **`void shutdown(uint32_t millis)`**: enter in shutdown mode
-**param** millis (optional): number of milliseconds before to exit the mode. At least 1000 ms. The RTC is used in alarm mode to wakeup the board in millis milliseconds.
+**param** millis (optional): number of milliseconds before to exit the mode. The RTC is used in alarm mode to wakeup the board in millis milliseconds.
 
 * **`void attachInterruptWakeup(uint32_t pin, voidFuncPtrVoid callback, uint32_t mode)`**: Enable GPIO pin in interrupt mode. If the pin is a wakeup pin, it is configured as wakeup source (see board documentation).  
 **param** pin: pin number  
diff --git a/src/STM32LowPower.cpp b/src/STM32LowPower.cpp
index f205373..fd7ff2e 100644
--- a/src/STM32LowPower.cpp
+++ b/src/STM32LowPower.cpp
@@ -169,13 +169,14 @@ void STM32LowPower::enableWakeupFrom(STM32RTC *rtc, voidFuncPtr callback, void *
 
 /**
   * @brief  Configure the RTC alarm
-  * @param  millis: time of the alarm in milliseconds. At least 1000ms.
+  * @param  millis: time of the alarm in milliseconds.
   * @param  lp_mode: low power mode targeted.
   * @retval None
   */
 void STM32LowPower::programRtcWakeUp(uint32_t millis, LP_Mode lp_mode)
 {
   int epoc;
+  uint32_t epoc_ms;
   uint32_t sec;
   STM32RTC &rtc = STM32RTC::getInstance();
   STM32RTC::Source_Clock clkSrc = rtc.getClockSource();
@@ -204,12 +205,17 @@ void STM32LowPower::programRtcWakeUp(uint32_t millis, LP_Mode lp_mode)
   if (millis > 0) {
     // Convert millisecond to second
     sec = millis / 1000;
-    // Minimum is 1 second
-    if (sec == 0) {
-      sec = 1;
+    millis = millis % 1000;
+
+    epoc = rtc.getEpoch(&epoc_ms);
+    
+    //Update epoch_ms - might need to add a second to epoch
+    epoc_ms += millis;
+    if (epoc_ms >= 1000) {
+      sec ++;
+      epoc_ms -= 1000;
     }
 
-    epoc = rtc.getEpoch();
-    rtc.setAlarmEpoch(epoc + sec);
+    rtc.setAlarmEpoch(epoc + sec, STM32RTC::MATCH_DHHMMSS, epoc_ms);
   }
 }