diff --git a/ivtest/vpi/sim_time_cb.c b/ivtest/vpi/sim_time_cb.c
new file mode 100644
index 000000000..acb829972
--- /dev/null
+++ b/ivtest/vpi/sim_time_cb.c
@@ -0,0 +1,171 @@
+#ifdef TEST_SCALED_TIME
+#define TIME_TYPE   vpiScaledRealTime
+#else
+#define TIME_TYPE   vpiSimTime
+#endif
+
+#include <vpi_user.h>
+#include <stdlib.h>
+#include <assert.h>
+
+static PLI_INT32 monitor_cb(p_cb_data cb_data)
+{
+    vpiHandle*var_list = (vpiHandle*)cb_data->user_data;
+
+    s_vpi_time  time;
+    s_vpi_value value;
+    PLI_INT32   index;
+
+    time.type = TIME_TYPE;
+    vpi_get_time(var_list[0], &time);
+#ifdef TEST_SCALED_TIME
+    vpi_printf(" @ %1.1f :", time.real);
+#else
+    vpi_printf(" @ %04d :", time.low);
+#endif
+
+    value.format = vpiIntVal;
+
+    index = 0;
+    while (var_list[index]) {
+        vpi_get_value(var_list[index], &value);
+        vpi_printf(" %s = %d", vpi_get_str(vpiName, var_list[index]), value.value.integer);
+        index++;
+    }
+    vpi_printf("\n");
+
+    return 0;
+}
+
+static PLI_INT32 monitor_cb_start(p_cb_data cb_data)
+{
+    vpi_printf("cbStartOfSimTime");
+    monitor_cb(cb_data);
+    return 0;
+}
+
+static PLI_INT32 monitor_cb_delay(p_cb_data cb_data)
+{
+    vpi_printf("cbAfterDelay    ");
+    monitor_cb(cb_data);
+    return 0;
+}
+
+static PLI_INT32 monitor_cb_synch(p_cb_data cb_data)
+{
+    vpi_printf("cbReadWriteSynch");
+    monitor_cb(cb_data);
+    return 0;
+}
+
+static PLI_INT32 monitor_cb_end(p_cb_data cb_data)
+{
+    vpiHandle*var_list = (vpiHandle*)cb_data->user_data;
+
+    vpi_printf("cbEndOfSimTime  ");
+    monitor_cb(cb_data);
+    free(var_list);
+    return 0;
+}
+
+static PLI_INT32 monitor_calltf(char*xx)
+{
+    vpiHandle sys  = vpi_handle(vpiSysTfCall, 0);
+    vpiHandle argv = vpi_iterate(vpiArgument, sys);
+
+    vpiHandle*var_list = 0;
+
+    vpiHandle   handle;
+    PLI_INT32   index;
+    s_vpi_time  time;
+    s_vpi_time  delay;
+    s_vpi_value value;
+    s_cb_data   cb_data;
+
+    (void)xx;  /* Parameter is not used. */
+
+    delay.type = TIME_TYPE;
+    delay.low  = 0;
+    delay.high = 0;
+    delay.real = 0.0;
+
+    assert(argv);
+    
+    handle = vpi_scan(argv);
+    assert(handle && (vpi_get(vpiType, handle) == vpiConstant));
+#ifdef TEST_SCALED_TIME
+    value.format = vpiRealVal;
+    vpi_get_value(handle, &value);
+    delay.real = value.value.real;
+#else
+    value.format = vpiIntVal;
+    vpi_get_value(handle, &value);
+    delay.low = value.value.integer;
+#endif
+
+    index = 0;
+    while ((handle = vpi_scan(argv))) {
+        assert(vpi_get(vpiType, handle) == vpiReg);
+        var_list = realloc(var_list, (index + 1) * sizeof(vpiHandle));
+        var_list[index++] = handle;
+    }
+    var_list = realloc(var_list, (index + 1) * sizeof(vpiHandle));
+    var_list[index++] = 0;
+
+    assert(index > 0);
+
+    time.type = TIME_TYPE;
+    vpi_get_time(var_list[0], &time);
+    // cbAtStartOfSimTime and cbAtEndOfSimTime want an absolute time.
+    // We know the test is short, so can ignore the high part.
+#ifdef TEST_SCALED_TIME
+    time.real += delay.real;
+#else
+    time.low += delay.low;
+#endif
+
+    cb_data.reason    = cbAtStartOfSimTime;
+    cb_data.cb_rtn    = monitor_cb_start;
+    cb_data.user_data = (char*)var_list;
+    cb_data.time      = &time;
+    vpi_register_cb(&cb_data);
+
+    cb_data.reason    = cbAfterDelay;
+    cb_data.cb_rtn    = monitor_cb_delay;
+    cb_data.user_data = (char*)var_list;
+    cb_data.time      = &delay;
+    vpi_register_cb(&cb_data);
+
+    // Add cbNBASynch when we support it
+
+    cb_data.reason    = cbReadWriteSynch;
+    cb_data.cb_rtn    = monitor_cb_synch;
+    cb_data.user_data = (char*)var_list;
+    cb_data.time      = &delay;
+    vpi_register_cb(&cb_data);
+
+    cb_data.reason    = cbAtEndOfSimTime;
+    cb_data.cb_rtn    = monitor_cb_end;
+    cb_data.user_data = (char*)var_list;
+    cb_data.time      = &time;
+    vpi_register_cb(&cb_data);
+
+    return 0;
+}
+
+static void monitor_register(void)
+{
+    s_vpi_systf_data tf_data;
+
+    tf_data.type      = vpiSysTask;
+    tf_data.tfname    = "$monitor_time_slot";
+    tf_data.calltf    = monitor_calltf;
+    tf_data.compiletf = 0;
+    tf_data.sizetf    = 0;
+    vpi_register_systf(&tf_data);
+}
+
+void (*vlog_startup_routines[])(void) = {
+    monitor_register,
+    0
+};
diff --git a/ivtest/vpi/sim_time_cb1.c b/ivtest/vpi/sim_time_cb1.c
new file mode 100644
index 000000000..d93ba2499
--- /dev/null
+++ b/ivtest/vpi/sim_time_cb1.c
@@ -0,0 +1,2 @@
+#define TEST_SIM_TIME
+#include "sim_time_cb.c"
diff --git a/ivtest/vpi/sim_time_cb1.v b/ivtest/vpi/sim_time_cb1.v
new file mode 100644
index 000000000..e58741bf3
--- /dev/null
+++ b/ivtest/vpi/sim_time_cb1.v
@@ -0,0 +1,27 @@
+`timescale 1s/1ms
+
+module test;
+
+reg [7:0] a, b;
+
+initial begin
+    a = 0; b = 0;
+    $monitor_time_slot(2000, a, b);
+    $monitor_time_slot(5000, a, b);
+    #1;
+    a = 1; b <= 1;
+    #1;
+    a = 2; b <= 2;
+    #1;
+    a = 3; b <= 3;
+    #1;
+    a = 4; b <= 4;
+    #1;
+    a = 5; b <= 5;
+    #1;
+    a = 6; b <= 6;
+    #1;
+    $finish(0);
+end
+
+endmodule
diff --git a/ivtest/vpi/sim_time_cb2.c b/ivtest/vpi/sim_time_cb2.c
new file mode 100644
index 000000000..dab1047ed
--- /dev/null
+++ b/ivtest/vpi/sim_time_cb2.c
@@ -0,0 +1,2 @@
+#define TEST_SCALED_TIME
+#include "sim_time_cb.c"
diff --git a/ivtest/vpi/sim_time_cb2.v b/ivtest/vpi/sim_time_cb2.v
new file mode 100644
index 000000000..cd547c2da
--- /dev/null
+++ b/ivtest/vpi/sim_time_cb2.v
@@ -0,0 +1,27 @@
+`timescale 1s/1ms
+
+module test;
+
+reg [7:0] a, b;
+
+initial begin
+    a = 0; b = 0;
+    $monitor_time_slot(2.0, a, b);
+    $monitor_time_slot(5.0, a, b);
+    #1;
+    a = 1; b <= 1;
+    #1;
+    a = 2; b <= 2;
+    #1;
+    a = 3; b <= 3;
+    #1;
+    a = 4; b <= 4;
+    #1;
+    a = 5; b <= 5;
+    #1;
+    a = 6; b <= 6;
+    #1;
+    $finish(0);
+end
+
+endmodule
diff --git a/ivtest/vpi_gold/sim_time_cb1.gold b/ivtest/vpi_gold/sim_time_cb1.gold
new file mode 100644
index 000000000..d99e5379b
--- /dev/null
+++ b/ivtest/vpi_gold/sim_time_cb1.gold
@@ -0,0 +1,10 @@
+Compiling vpi/sim_time_cb1.c...
+Making sim_time_cb1.vpi from  sim_time_cb1.o...
+cbStartOfSimTime @ 2000 : a = 1 b = 1
+cbAfterDelay     @ 2000 : a = 1 b = 1
+cbReadWriteSynch @ 2000 : a = 2 b = 2
+cbEndOfSimTime   @ 2000 : a = 2 b = 2
+cbStartOfSimTime @ 5000 : a = 4 b = 4
+cbAfterDelay     @ 5000 : a = 4 b = 4
+cbReadWriteSynch @ 5000 : a = 5 b = 5
+cbEndOfSimTime   @ 5000 : a = 5 b = 5
diff --git a/ivtest/vpi_gold/sim_time_cb2.gold b/ivtest/vpi_gold/sim_time_cb2.gold
new file mode 100644
index 000000000..0ec0e5ae1
--- /dev/null
+++ b/ivtest/vpi_gold/sim_time_cb2.gold
@@ -0,0 +1,10 @@
+Compiling vpi/sim_time_cb2.c...
+Making sim_time_cb2.vpi from  sim_time_cb2.o...
+cbStartOfSimTime @ 2.0 : a = 1 b = 1
+cbAfterDelay     @ 2.0 : a = 1 b = 1
+cbReadWriteSynch @ 2.0 : a = 2 b = 2
+cbEndOfSimTime   @ 2.0 : a = 2 b = 2
+cbStartOfSimTime @ 5.0 : a = 4 b = 4
+cbAfterDelay     @ 5.0 : a = 4 b = 4
+cbReadWriteSynch @ 5.0 : a = 5 b = 5
+cbEndOfSimTime   @ 5.0 : a = 5 b = 5
diff --git a/ivtest/vpi_regress.list b/ivtest/vpi_regress.list
index facced0c6..24c928180 100644
--- a/ivtest/vpi_regress.list
+++ b/ivtest/vpi_regress.list
@@ -132,6 +132,8 @@ scanmem			normal			scanmem.cc		scanmem.log
 scanmem2		normal			scanmem2.cc		scanmem2.log
 scanmem3		normal			scanmem3.cc		scanmem3.log
 scopes			normal			scopes.c		scopes.log
+sim_time_cb1		normal			sim_time_cb1.c		sim_time_cb1.gold
+sim_time_cb2		normal			sim_time_cb2.c		sim_time_cb2.gold
 spec_delays		normal,-gspecify	spec_delays.c		spec_delays.log
 start_of_simtime1	normal			start_of_simtime1.c	start_of_simtime1.log
 timescale		normal			timescale.c		timescale.log