diff --git a/master/fsm_master.c b/master/fsm_master.c
index 0388096c..e9ec0c88 100644
--- a/master/fsm_master.c
+++ b/master/fsm_master.c
@@ -960,7 +960,7 @@ void ec_fsm_master_enter_write_system_times(
 {
     ec_master_t *master = fsm->master;
 
-    if (master->has_app_time) {
+    if (master->dc_ref_time) {
 
         while (fsm->slave < master->slaves + master->slave_count) {
             if (!fsm->slave->base_dc_supported
@@ -984,7 +984,7 @@ void ec_fsm_master_enter_write_system_times(
 
     } else {
         if (master->active) {
-            EC_MASTER_WARN(master, "No app_time received up to now,"
+            EC_MASTER_WARN(master, "No application time received up to now,"
                     " but master already active.\n");
         } else {
             EC_MASTER_DBG(master, 1, "No app_time received up to now.\n");
diff --git a/master/fsm_slave_config.c b/master/fsm_slave_config.c
index 5c968768..25ffdd1d 100644
--- a/master/fsm_slave_config.c
+++ b/master/fsm_slave_config.c
@@ -1413,30 +1413,28 @@ void ec_fsm_slave_config_state_dc_sync_check(
                 abs_sync_diff, diff_ms);
     }
 
-    // set DC start time
+    // set DC start time (roughly in the future, not in-phase)
     start_time = master->app_time + EC_DC_START_OFFSET; // now + X ns
-    // FIXME use slave's local system time here?
 
     if (sync0->cycle_time) {
         // find correct phase
-        if (master->has_app_time) {
+        if (master->dc_ref_time) {
             u64 diff, start;
             u32 remainder, cycle;
 
-            diff = start_time - master->app_start_time;
+            diff = start_time - master->dc_ref_time;
             cycle = sync0->cycle_time + sync1->cycle_time;
             remainder = do_div(diff, cycle);
 
             start = start_time + cycle - remainder + sync0->shift_time;
 
-            EC_SLAVE_DBG(slave, 1, "app_start_time=%llu\n",
-                    master->app_start_time);
-            EC_SLAVE_DBG(slave, 1, "      app_time=%llu\n", master->app_time);
-            EC_SLAVE_DBG(slave, 1, "    start_time=%llu\n", start_time);
-            EC_SLAVE_DBG(slave, 1, "         cycle=%u\n", cycle);
-            EC_SLAVE_DBG(slave, 1, "    shift_time=%i\n", sync0->shift_time);
-            EC_SLAVE_DBG(slave, 1, "     remainder=%u\n", remainder);
-            EC_SLAVE_DBG(slave, 1, "         start=%llu\n", start);
+            EC_SLAVE_DBG(slave, 1, "   ref_time=%llu\n", master->dc_ref_time);
+            EC_SLAVE_DBG(slave, 1, "   app_time=%llu\n", master->app_time);
+            EC_SLAVE_DBG(slave, 1, " start_time=%llu\n", start_time);
+            EC_SLAVE_DBG(slave, 1, "      cycle=%u\n", cycle);
+            EC_SLAVE_DBG(slave, 1, " shift_time=%i\n", sync0->shift_time);
+            EC_SLAVE_DBG(slave, 1, "  remainder=%u\n", remainder);
+            EC_SLAVE_DBG(slave, 1, "       start=%llu\n", start);
             start_time = start;
         } else {
             EC_SLAVE_WARN(slave, "No application time supplied."
diff --git a/master/ioctl.c b/master/ioctl.c
index 30fa2f5c..d4d4cd49 100644
--- a/master/ioctl.c
+++ b/master/ioctl.c
@@ -180,6 +180,7 @@ static ATTRIBUTES int ec_ioctl_master(
     up(&master->device_sem);
 
     io.app_time = master->app_time;
+    io.dc_ref_time = master->dc_ref_time;
     io.ref_clock =
         master->dc_ref_clock ? master->dc_ref_clock->ring_position : 0xffff;
 
diff --git a/master/ioctl.h b/master/ioctl.h
index 30969741..fcf894b9 100644
--- a/master/ioctl.h
+++ b/master/ioctl.h
@@ -56,7 +56,7 @@
  *
  * Increment this when changing the ioctl interface!
  */
-#define EC_IOCTL_VERSION_MAGIC 28
+#define EC_IOCTL_VERSION_MAGIC 29
 
 // Command-line tool
 #define EC_IOCTL_MODULE                EC_IOR(0x00, ec_ioctl_module_t)
@@ -201,6 +201,7 @@ typedef struct {
     int32_t rx_byte_rates[EC_RATE_COUNT];
     int32_t loss_rates[EC_RATE_COUNT];
     uint64_t app_time;
+    uint64_t dc_ref_time;
     uint16_t ref_clock;
 } ec_ioctl_master_t;
 
diff --git a/master/master.c b/master/master.c
index 86532a51..38a323ca 100644
--- a/master/master.c
+++ b/master/master.c
@@ -184,8 +184,7 @@ int ec_master_init(ec_master_t *master, /**< EtherCAT master */
     INIT_LIST_HEAD(&master->domains);
 
     master->app_time = 0ULL;
-    master->app_start_time = 0ULL;
-    master->has_app_time = 0;
+    master->dc_ref_time = 0ULL;
 
     master->scan_busy = 0;
     master->allow_scan = 1;
@@ -2417,8 +2416,7 @@ void ecrt_master_deactivate(ec_master_t *master)
 #endif
 
     master->app_time = 0ULL;
-    master->app_start_time = 0ULL;
-    master->has_app_time = 0;
+    master->dc_ref_time = 0ULL;
 
 #ifdef EC_EOE
     if (eoe_was_running) {
@@ -2774,9 +2772,8 @@ void ecrt_master_application_time(ec_master_t *master, uint64_t app_time)
 {
     master->app_time = app_time;
 
-    if (unlikely(!master->has_app_time)) {
-        master->app_start_time = app_time;
-        master->has_app_time = 1;
+    if (unlikely(!master->dc_ref_time)) {
+        master->dc_ref_time = app_time;
     }
 }
 
diff --git a/master/master.h b/master/master.h
index ddd7c8d7..98e9fdf9 100644
--- a/master/master.h
+++ b/master/master.h
@@ -236,8 +236,7 @@ struct ec_master {
     struct list_head domains; /**< List of domains. */
 
     u64 app_time; /**< Time of the last ecrt_master_sync() call. */
-    u64 app_start_time; /**< Application start time. */
-    u8 has_app_time; /**< Application time is valid. */
+    u64 dc_ref_time; /**< Common reference timestamp for DC start times. */
     ec_datagram_t ref_sync_datagram; /**< Datagram used for synchronizing the
                                        reference clock to the master clock. */
     ec_datagram_t sync_datagram; /**< Datagram used for DC drift
diff --git a/tool/CommandMaster.cpp b/tool/CommandMaster.cpp
index bd84609f..38b7dd9d 100644
--- a/tool/CommandMaster.cpp
+++ b/tool/CommandMaster.cpp
@@ -264,6 +264,7 @@ void CommandMaster::execute(const StringVector &args)
             cout << "None";
         }
         cout << endl
+            << "    DC reference time: " << data.dc_ref_time << endl
             << "    Application time: " << data.app_time << endl
             << "                      ";