diff --git a/src/conf/schemas/domaincommon.rng b/src/conf/schemas/domaincommon.rng
index ebb39de3ef..cefe818044 100644
--- a/src/conf/schemas/domaincommon.rng
+++ b/src/conf/schemas/domaincommon.rng
@@ -1312,7 +1312,7 @@
               <value>absolute</value>
             </attribute>
             <attribute name="start">
-              <ref name="unsignedInt"/>
+              <ref name="unsignedLong"/>
             </attribute>
           </group>
         </choice>
diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c
index 1456a69351..1d4081e47e 100644
--- a/src/qemu/qemu_validate.c
+++ b/src/qemu/qemu_validate.c
@@ -663,6 +663,23 @@ qemuValidateDomainDefClockTimers(const virDomainDef *def,
         }
     }
 
+    switch ((virDomainClockOffsetType) def->clock.offset) {
+    case VIR_DOMAIN_CLOCK_OFFSET_ABSOLUTE:
+        /* maximum timestamp glib can convert is 9999-12-31T23:59:59 */
+        if (def->clock.data.starttime > 253402300799) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("The maximum 'start' value for <clock offset='absolute'> is 253402300799"));
+            return -1;
+        }
+
+    case VIR_DOMAIN_CLOCK_OFFSET_UTC:
+    case VIR_DOMAIN_CLOCK_OFFSET_LOCALTIME:
+    case VIR_DOMAIN_CLOCK_OFFSET_TIMEZONE:
+    case VIR_DOMAIN_CLOCK_OFFSET_VARIABLE:
+    case VIR_DOMAIN_CLOCK_OFFSET_LAST:
+        break;
+    }
+
     return 0;
 }
 
diff --git a/tests/qemuxml2argvdata/clock-absolute.x86_64-latest.args b/tests/qemuxml2argvdata/clock-absolute.x86_64-latest.args
index 75fc162cee..af64bc0f1a 100644
--- a/tests/qemuxml2argvdata/clock-absolute.x86_64-latest.args
+++ b/tests/qemuxml2argvdata/clock-absolute.x86_64-latest.args
@@ -23,7 +23,7 @@ XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
 -nodefaults \
 -chardev socket,id=charmonitor,fd=1729,server=on,wait=off \
 -mon chardev=charmonitor,id=monitor,mode=control \
--rtc base=1970-01-01T00:20:34 \
+-rtc base=9999-12-31T23:59:59 \
 -no-shutdown \
 -no-acpi \
 -boot strict=on \
diff --git a/tests/qemuxml2argvdata/clock-absolute.xml b/tests/qemuxml2argvdata/clock-absolute.xml
index e79f53ed3c..63ef7f6f33 100644
--- a/tests/qemuxml2argvdata/clock-absolute.xml
+++ b/tests/qemuxml2argvdata/clock-absolute.xml
@@ -8,7 +8,7 @@
     <type arch='x86_64' machine='pc'>hvm</type>
     <boot dev='hd'/>
   </os>
-  <clock offset='absolute' start='1234'/>
+  <clock offset='absolute' start='253402300799'/>
   <on_poweroff>destroy</on_poweroff>
   <on_reboot>restart</on_reboot>
   <on_crash>destroy</on_crash>
diff --git a/tests/qemuxml2xmloutdata/clock-absolute.x86_64-latest.xml b/tests/qemuxml2xmloutdata/clock-absolute.x86_64-latest.xml
index b313a74039..eea68677d5 100644
--- a/tests/qemuxml2xmloutdata/clock-absolute.x86_64-latest.xml
+++ b/tests/qemuxml2xmloutdata/clock-absolute.x86_64-latest.xml
@@ -11,7 +11,7 @@
   <cpu mode='custom' match='exact' check='none'>
     <model fallback='forbid'>qemu64</model>
   </cpu>
-  <clock offset='absolute' start='1234'/>
+  <clock offset='absolute' start='253402300799'/>
   <on_poweroff>destroy</on_poweroff>
   <on_reboot>restart</on_reboot>
   <on_crash>destroy</on_crash>