diff --git a/DS2417.pdf b/DS2417.pdf
new file mode 100644
index 0000000..1dd9bc8
Binary files /dev/null and b/DS2417.pdf differ
diff --git a/main.c b/main.c
index ce48ceb..6bebd39 100644
--- a/main.c
+++ b/main.c
@@ -2,6 +2,8 @@
 #include <conio.h>
 #include "ow.h"
 #include "ow-temp.h"
+#include "ow-time.h"
+#include <errno.h>
 
 int main (void)
 {
@@ -9,24 +11,46 @@ int main (void)
   unsigned char devs[80];
   unsigned char* tempsensor=NULL;
   unsigned char* clock=NULL;
+  time_t t;
+//  unsigned char c1, c2;
 
   devcount=ow_enumeratedevices(devs, 10);
+
+/*//
+  for (c1=0; c1<devcount; c1++)
+  {
+    printf("%i: ", c1);
+    for (c2=0; c2<8; c2++)
+      printf("%02X ", devs[(c1<<3)+c2]);
+    printf("\n");
+  }
+//*/
+
   for (i=0; i<devcount; i++)
+  {
     if (ow_temp_idcheck(&devs[i<<3]))
       tempsensor=&devs[i<<3];
-  if (tempsensor==NULL)
+    if (ow_time_idcheck(&devs[i<<3]))
+      clock=&devs[i<<3];
+  }
+  if (tempsensor==NULL || clock==NULL)
   {
-    printf("Error: no temperature sensor found.\n");
+    printf("Error: temperature sensor and/or clock not found.\n");
     return -1;
   }
 
+  ow_time_set(clock, 1190611728-28800);
+  
   do
   {
     do
     {
       for (i=0; i<250; i++)
         ow_mswait();
-      printf("%i deg F\n", ow_temp_read(tempsensor, OW_TEMP_FAHRENHEIT));
+      t=ow_time_read(clock);
+      printf("%i deg F %s", 
+        ow_temp_read(tempsensor, OW_TEMP_FAHRENHEIT), 
+        asctime(localtime(&t)));
     }
     while (!kbhit());
   }
diff --git a/ow-temp.c b/ow-temp.c
index aa6bd65..a76e29d 100644
--- a/ow-temp.c
+++ b/ow-temp.c
@@ -1,4 +1,5 @@
 #include "ow-temp.h"
+#include <errno.h>
 
 short ow_temp_read(unsigned char* devid, unsigned char format)
 {
@@ -7,7 +8,10 @@ short ow_temp_read(unsigned char* devid, unsigned char format)
   unsigned char i;
 
   if (!ow_temp_idcheck(devid))
-    return OW_ERR_INVALIDDEVICE;
+  {
+    errno=EINVAL;
+    return -1;
+  }
   ow_selectdevice(devid);
   ow_writebyte(68); // ask for a temperature reading
   ow_wait(); // wait for operation to complete
@@ -17,6 +21,7 @@ short ow_temp_read(unsigned char* devid, unsigned char format)
     data[i]=ow_readbyte();
   
   rawtemp=(short)(data[0]+((int)data[1]<<8));
+  errno=0;
   switch (format)
   {
   case OW_TEMP_FAHRENHEIT:
diff --git a/ow-time.c b/ow-time.c
new file mode 100644
index 0000000..58fb8b5
--- /dev/null
+++ b/ow-time.c
@@ -0,0 +1,46 @@
+#include "ow-time.h"
+#include <errno.h>
+
+time_t ow_time_read(unsigned char* devid)
+{
+  time_t t;
+  unsigned char i;
+  
+  if (!ow_time_idcheck(devid))
+  {
+    errno=EINVAL;
+    return -1;
+  }
+  ow_selectdevice(devid);
+  ow_writebyte(102); // read clock
+  ow_readbyte(); // skip first byte returned
+  for (i=0; i<4; i++) // read time
+    ((unsigned char*)&t)[i]=ow_readbyte();
+  ow_reset();
+  errno=0;
+  return t;    
+}
+
+void ow_time_set(unsigned char* devid, time_t newtime)
+{
+  unsigned char i;
+  
+  if (!ow_time_idcheck(devid))
+  {
+    errno=EINVAL;
+    return;
+  }
+  ow_selectdevice(devid);
+  ow_writebyte(153); // set clock
+  ow_writebyte(12); // device control: start oscillator
+  for (i=0; i<4; i++) // write time
+    ow_writebyte(((unsigned char*)&newtime)[i]);
+  ow_reset();
+  errno=0;
+  return;
+}
+
+unsigned char ow_time_idcheck(unsigned char* devid)
+{
+  return (devid[0]==39)?1:0;
+}
diff --git a/ow-time.h b/ow-time.h
new file mode 100644
index 0000000..cbd0b07
--- /dev/null
+++ b/ow-time.h
@@ -0,0 +1,13 @@
+#ifndef OW_TIME_H
+#define OW_TIME_H
+
+#include "ow.h"
+#include <time.h>
+
+// 1-Wire real-time clock functions
+
+time_t ow_time_read(unsigned char* devid);
+void ow_time_set(unsigned char* devid, time_t newtime);
+unsigned char ow_time_idcheck(unsigned char* devid);
+
+#endif // OW_TIME_H
diff --git a/ow.h b/ow.h
index e1fdb71..014c373 100644
--- a/ow.h
+++ b/ow.h
@@ -17,8 +17,4 @@ void ow_selectdevice(unsigned char* devid);
 unsigned char ow_crc(unsigned char* data, unsigned char len);
 unsigned char ow_enumeratedevices(unsigned char* devids, unsigned char maxdevs);
 
-// common 1-Wire constants
-
-#define OW_ERR_INVALIDDEVICE -32767
-
 #endif // OW_H