diff --git a/src/lib/ebus/datatype.cpp b/src/lib/ebus/datatype.cpp
index 59a62ce1..6a5c62ff 100755
--- a/src/lib/ebus/datatype.cpp
+++ b/src/lib/ebus/datatype.cpp
@@ -345,11 +345,11 @@ result_t DateTimeDataType::readSymbols(size_t offset, size_t length, const Symbo
     }
     switch (type) {
       case 2:  // date only
-        if (!hasFlag(REQ) && symbol == m_replacement) {
+        if (!hasFlag(REQ) && (symbol == m_replacement || (!hasFlag(REZ) && symbol == 0))) {
           if (i + 1 != length) {
             *output << NULL_VALUE << ".";
             break;
-          } else if (last == m_replacement) {
+          } else if (last == m_replacement || (!hasFlag(REZ) && last == 0)) {
             if (length == 2) {  // number of days since 01.01.1900
               *output << NULL_VALUE << ".";
             }
@@ -1228,7 +1228,7 @@ DataTypeList::DataTypeList() {
   // date, 01.01.2000 - 31.12.2099 (0x01,0x01,0x00 - 0x1f,0x0c,0x63, replacement 0xff)
   add(new DateTimeDataType("HDA:3", 24, 0, 0xff, true, false, 0));
   // date, days since 01.01.1900, 01.01.1900 - 06.06.2079 (0x00,0x00 - 0xff,0xff)
-  add(new DateTimeDataType("DAY", 16, 0, 0xff, true, false, 0));
+  add(new DateTimeDataType("DAY", 16, REZ, 0xff, true, false, 0));
   // date+time in minutes since 01.01.2009, 01.01.2009 - 31.12.2099 (0x00,0x00,0x00,0x00 - 0x02,0xda,0x4e,0x1f)
   add(new DateTimeDataType("DTM", 32, REQ, 0x100, true, true, 0));
   // time in BCD, 00:00:00 - 23:59:59 (0x00,0x00,0x00 - 0x59,0x59,0x23)
diff --git a/src/lib/ebus/datatype.h b/src/lib/ebus/datatype.h
index f6bd1a23..c5e77a46 100755
--- a/src/lib/ebus/datatype.h
+++ b/src/lib/ebus/datatype.h
@@ -194,6 +194,9 @@ enum PartType {
 /** bit flag for @a DataType: stored duplicate for backwards compatibility, not to be traversed in lists any more. */
 #define DUP 0x2000
 
+/** bit flag for @a DataType: special marker for non-tolerated secondary replacement value of zero (date only). */
+#define REZ 0x4000
+
 /**
  * Parse a float value from the 32 bit representation (IEEE 754).
  * @param value the 32 bit representation of the float value.
diff --git a/src/lib/ebus/test/test_data.cpp b/src/lib/ebus/test/test_data.cpp
index fc44392a..1c09989d 100755
--- a/src/lib/ebus/test/test_data.cpp
+++ b/src/lib/ebus/test/test_data.cpp
@@ -143,11 +143,13 @@ int main() {
       {"x,,bda",   "20.02.2021", "10fe07000420020621", "00", ""},  // Saturday
       {"x,,bda",   "31.12.2099", "10fe07000431120499", "00", ""},  // Thursday
       {"x,,bda",   "-.-.-",      "10fe070004ffff00ff", "00", ""},
+      {"x,,bda",   "-.-.-",      "10fe07000400000000", "00", "W"},
       {"x,,bda",   "",           "10fe07000432100014", "00", "rw"},
       {"x,,bda:3", "26.10.2014", "10fe070003261014",   "00", ""},
       {"x,,bda:3", "01.01.2000", "10fe070003010100",   "00", ""},
       {"x,,bda:3", "31.12.2099", "10fe070003311299",   "00", ""},
       {"x,,bda:3", "-.-.-",      "10fe070003ffffff",   "00", ""},
+      {"x,,bda:3", "-.-.-",      "10fe070003000000",   "00", "W"},
       {"x,,bda:3", "",           "10fe070003321299",   "00", "rw"},
       {"x,,bda,2", "",           "",                   "",   "c"},
       {"x,,bdz",   "26.10.2014", "10fe07000426100614", "00", ""},  // Sunday
@@ -155,16 +157,19 @@ int main() {
       {"x,,bdz",   "20.02.2021", "10fe07000420020521", "00", ""},  // Saturday
       {"x,,bdz",   "31.12.2099", "10fe07000431120399", "00", ""},  // Thursday
       {"x,,bdz",   "-.-.-",      "10fe070004ffff00ff", "00", ""},
+      {"x,,bdz",   "-.-.-",      "10fe07000400000000", "00", "W"},
       {"x,,bdz",   "",           "10fe07000432100014", "00", "rw"},
       {"x,,hda",   "26.10.2014", "10fe0700041a0a070e", "00", ""},  // Sunday
       {"x,,hda",   "01.01.2000", "10fe07000401010600", "00", ""},  // Saturday
       {"x,,hda",   "31.12.2099", "10fe0700041f0c0463", "00", ""},  // Thursday
       {"x,,hda",   "-.-.-",      "10fe070004ffff00ff", "00", ""},
+      {"x,,hda",   "-.-.-",      "10fe07000400000000", "00", "W"},
       {"x,,hda",   "",           "10fe070004200c0463", "00", "rw"},
       {"x,,hda:3", "26.10.2014", "10fe0700031a0a0e",   "00", ""},
       {"x,,hda:3", "01.01.2000", "10fe070003010100",   "00", ""},
       {"x,,hda:3", "31.12.2099", "10fe0700031f0c63",   "00", ""},
       {"x,,hda:3", "-.-.-",      "10fe070003ffffff",   "00", ""},
+      {"x,,hda:3", "-.-.-",      "10fe070003000000",   "00", "W"},
       {"x,,hda:3", "",           "10fe070003200c63",   "00", "rw"},
       {"x,,hda,2", "",           "",                   "",   "c"},
       {"x,,day",   "26.10.2014", "10fe070002d0a3", "00", ""},