diff --git a/drivers/timer/legacy_api.h b/drivers/timer/legacy_api.h
index de1990c76bc..84da6350a0f 100644
--- a/drivers/timer/legacy_api.h
+++ b/drivers/timer/legacy_api.h
@@ -1,10 +1,11 @@
 #ifndef ZEPHYR_LEGACY_SET_TIME_H__
 #define ZEPHYR_LEGACY_SET_TIME_H__
 
-/* Stub implementation of z_clock_set_timeout() in terms of the
- * original APIs.  Used by older timer drivers.  Should be replaced.
+/* Stub implementation of z_clock_set_timeout() and z_clock_elapsed()
+ * in terms of the original APIs.  Used by older timer drivers.
+ * Should be replaced.
  *
- * Yes, this "header" includes a function definition and must be
+ * Yes, this "header" includes function definitions and must be
  * included only once in a single compilation.
  */
 
@@ -20,7 +21,9 @@ extern u32_t _get_remaining_program_time(void);
 extern u32_t _get_elapsed_program_time(void);
 #endif
 
-extern void z_clock_set_timeout(s32_t ticks, bool idle)
+extern u64_t z_clock_uptime(void);
+
+void z_clock_set_timeout(s32_t ticks, bool idle)
 {
 #ifdef CONFIG_TICKLESS_KERNEL
 	if (idle) {
@@ -31,4 +34,24 @@ extern void z_clock_set_timeout(s32_t ticks, bool idle)
 #endif
 }
 
+/* The old driver "now" API would return a full uptime value.  The new
+ * one only requires the driver to track ticks since the last announce
+ * call.  Implement the new call in terms of the old one on legacy
+ * drivers by keeping (yet another) uptime value locally.
+ */
+static u32_t driver_uptime;
+
+u32_t z_clock_elapsed(void)
+{
+	return (u32_t)(z_clock_uptime() - driver_uptime);
+}
+
+static void wrapped_announce(s32_t ticks)
+{
+	driver_uptime += ticks;
+	z_clock_announce(ticks);
+}
+
+#define z_clock_announce(t) wrapped_announce(t)
+
 #endif /* ZEPHYR_LEGACY_SET_TIME_H__ */
diff --git a/drivers/timer/pulpino_timer.c b/drivers/timer/pulpino_timer.c
index effa0da2e12..513479279ba 100644
--- a/drivers/timer/pulpino_timer.c
+++ b/drivers/timer/pulpino_timer.c
@@ -72,3 +72,8 @@ u32_t _timer_cycle_get_32(void)
 {
 	return accumulated_cycle_count + timer->val;
 }
+
+u32_t z_clock_elapsed(void)
+{
+	return 0;
+}
diff --git a/include/drivers/system_timer.h b/include/drivers/system_timer.h
index 04da471413d..48a13f51617 100644
--- a/include/drivers/system_timer.h
+++ b/include/drivers/system_timer.h
@@ -102,12 +102,14 @@ extern void z_clock_idle_exit(void);
 extern void z_clock_announce(s32_t ticks);
 
 /**
- * @brief System uptime in ticks
+ * @brief Ticks elapsed since last z_clock_announce() call
  *
- * Queries the clock driver for the current time elapsed since system
- * bootup in ticks.
+ * Queries the clock driver for the current time elapsed since the
+ * last call to z_clock_announce() was made.  The kernel will call
+ * this with appropriate locking, the driver needs only provide an
+ * instantaneous answer.
  */
-extern u64_t z_clock_uptime(void);
+extern u32_t z_clock_elapsed(void);
 
 #ifdef __cplusplus
 }
diff --git a/kernel/sys_clock.c b/kernel/sys_clock.c
index 9e5900b246c..5c7e5f3b76d 100644
--- a/kernel/sys_clock.c
+++ b/kernel/sys_clock.c
@@ -31,6 +31,8 @@ int z_clock_hw_cycles_per_sec;
 #endif
 #endif
 
+extern u64_t z_clock_uptime(void);
+
 /* Note that this value is 64 bits, and thus non-atomic on almost all
  * Zephyr archtictures.  And of course it's routinely updated inside
  * timer interrupts.  Access to it must be locked.