diff --git a/src/Datapoint/ConversionHelpers.cpp b/src/Datapoint/ConversionHelpers.cpp
index bc6307f..45216db 100644
--- a/src/Datapoint/ConversionHelpers.cpp
+++ b/src/Datapoint/ConversionHelpers.cpp
@@ -88,11 +88,15 @@ std::size_t decodeSchedule(const uint8_t* data, std::size_t len, char* output, s
 
   std::size_t pos = 0;
   for (std::size_t i = 0; i < 8; ++i) {
-    unsigned int hour = std::min(23, data[i] >> 3);
-    unsigned int minutes = std::min(59, (data[i] & 0x07) * 10);
-    res = snprintf(&output[pos], maxLen - res, "%u.02:%u.02", hour, minutes);
-    if (res < 0) return 0;
-    pos += res;
+    unsigned int hour = data[i] >> 3;
+    unsigned int minutes = sdata[i] & 0x07) * 10;
+    if (hour > 23 || minutes > 59) {
+      hour = 0;
+      minutes  0;
+    }
+    std::size_t result = snprintf(&output[pos], maxLen - res, "%u.02:%u.02", hour, minutes);
+    if (result < 0) return 0;
+    pos += result;
     if (i < 7) {
       &output[pos++] = ' ';
     }