diff --git a/system_wrappers/BUILD.gn b/system_wrappers/BUILD.gn
index 7059fac740..1f17a94209 100644
--- a/system_wrappers/BUILD.gn
+++ b/system_wrappers/BUILD.gn
@@ -32,6 +32,7 @@ rtc_static_library("system_wrappers") {
   deps = [
     ":cpu_features_api",
     "../api:array_view",
+    "../api/units:timestamp",
     "../modules:module_api_public",
     "../rtc_base:checks",
     "../rtc_base/synchronization:rw_lock_wrapper",
diff --git a/system_wrappers/include/clock.h b/system_wrappers/include/clock.h
index b2c6c5fddb..09d2785179 100644
--- a/system_wrappers/include/clock.h
+++ b/system_wrappers/include/clock.h
@@ -14,6 +14,7 @@
 #include <stdint.h>
 #include <memory>
 
+#include "api/units/timestamp.h"
 #include "rtc_base/synchronization/rw_lock_wrapper.h"
 #include "system_wrappers/include/ntp_time.h"
 
@@ -29,14 +30,12 @@ const double kMagicNtpFractionalUnit = 4.294967296E+9;
 class Clock {
  public:
   virtual ~Clock() {}
-
-  // Return a timestamp in milliseconds relative to some arbitrary source; the
-  // source is fixed for this clock.
-  virtual int64_t TimeInMilliseconds() = 0;
-
-  // Return a timestamp in microseconds relative to some arbitrary source; the
-  // source is fixed for this clock.
-  virtual int64_t TimeInMicroseconds() = 0;
+  // Return a timestamp relative to an unspecified epoch.
+  virtual Timestamp CurrentTime() {
+    return Timestamp::us(TimeInMicroseconds());
+  }
+  virtual int64_t TimeInMilliseconds() { return CurrentTime().ms(); }
+  virtual int64_t TimeInMicroseconds() { return CurrentTime().us(); }
 
   // Retrieve an NTP absolute timestamp.
   virtual NtpTime CurrentNtpTime() = 0;
@@ -56,16 +55,13 @@ class Clock {
 class SimulatedClock : public Clock {
  public:
   explicit SimulatedClock(int64_t initial_time_us);
+  explicit SimulatedClock(Timestamp initial_time);
 
   ~SimulatedClock() override;
 
-  // Return a timestamp in milliseconds relative to some arbitrary source; the
-  // source is fixed for this clock.
-  int64_t TimeInMilliseconds() override;
-
-  // Return a timestamp in microseconds relative to some arbitrary source; the
-  // source is fixed for this clock.
-  int64_t TimeInMicroseconds() override;
+  // Return a timestamp relative to some arbitrary source; the source is fixed
+  // for this clock.
+  Timestamp CurrentTime() override;
 
   // Retrieve an NTP absolute timestamp.
   NtpTime CurrentNtpTime() override;
@@ -77,9 +73,10 @@ class SimulatedClock : public Clock {
   // microseconds.
   void AdvanceTimeMilliseconds(int64_t milliseconds);
   void AdvanceTimeMicroseconds(int64_t microseconds);
+  void AdvanceTime(TimeDelta delta);
 
  private:
-  int64_t time_us_;
+  Timestamp time_;
   std::unique_ptr<RWLockWrapper> lock_;
 };
 
diff --git a/system_wrappers/source/clock.cc b/system_wrappers/source/clock.cc
index f69d13c1db..3eea155711 100644
--- a/system_wrappers/source/clock.cc
+++ b/system_wrappers/source/clock.cc
@@ -32,6 +32,7 @@
 namespace webrtc {
 
 class RealTimeClock : public Clock {
+  Timestamp CurrentTime() override { return Timestamp::us(rtc::TimeMicros()); }
   // Return a timestamp in milliseconds relative to some arbitrary source; the
   // source is fixed for this clock.
   int64_t TimeInMilliseconds() override { return rtc::TimeMillis(); }
@@ -236,18 +237,16 @@ Clock* Clock::GetRealTimeClock() {
 }
 
 SimulatedClock::SimulatedClock(int64_t initial_time_us)
-    : time_us_(initial_time_us), lock_(RWLockWrapper::CreateRWLock()) {}
+    : SimulatedClock(Timestamp::us(initial_time_us)) {}
+
+SimulatedClock::SimulatedClock(Timestamp initial_time)
+    : time_(initial_time), lock_(RWLockWrapper::CreateRWLock()) {}
 
 SimulatedClock::~SimulatedClock() {}
 
-int64_t SimulatedClock::TimeInMilliseconds() {
+Timestamp SimulatedClock::CurrentTime() {
   ReadLockScoped synchronize(*lock_);
-  return (time_us_ + 500) / 1000;
-}
-
-int64_t SimulatedClock::TimeInMicroseconds() {
-  ReadLockScoped synchronize(*lock_);
-  return time_us_;
+  return time_;
 }
 
 NtpTime SimulatedClock::CurrentNtpTime() {
@@ -263,12 +262,16 @@ int64_t SimulatedClock::CurrentNtpInMilliseconds() {
 }
 
 void SimulatedClock::AdvanceTimeMilliseconds(int64_t milliseconds) {
-  AdvanceTimeMicroseconds(1000 * milliseconds);
+  AdvanceTime(TimeDelta::ms(milliseconds));
 }
 
 void SimulatedClock::AdvanceTimeMicroseconds(int64_t microseconds) {
+  AdvanceTime(TimeDelta::us(microseconds));
+}
+
+void SimulatedClock::AdvanceTime(TimeDelta delta) {
   WriteLockScoped synchronize(*lock_);
-  time_us_ += microseconds;
+  time_ += delta;
 }
 
 }  // namespace webrtc
diff --git a/test/drifting_clock.cc b/test/drifting_clock.cc
index 41ab2cf59e..2907ad0ec2 100644
--- a/test/drifting_clock.cc
+++ b/test/drifting_clock.cc
@@ -18,25 +18,19 @@ const float DriftingClock::kNoDrift = 1.0f;
 const float DriftingClock::kHalfSpeed = 0.5f;
 
 DriftingClock::DriftingClock(Clock* clock, float speed)
-    : clock_(clock),
-      drift_(speed - 1.0f),
-      start_time_(clock_->TimeInMicroseconds()) {
+    : clock_(clock), drift_(speed - 1.0f), start_time_(clock_->CurrentTime()) {
   RTC_CHECK(clock);
   RTC_CHECK_GT(speed, 0.0f);
 }
 
-float DriftingClock::Drift() const {
-  int64_t now = clock_->TimeInMicroseconds();
+TimeDelta DriftingClock::Drift() const {
+  auto now = clock_->CurrentTime();
   RTC_DCHECK_GE(now, start_time_);
   return (now - start_time_) * drift_;
 }
 
-int64_t DriftingClock::TimeInMilliseconds() {
-  return clock_->TimeInMilliseconds() + Drift() / 1000.;
-}
-
-int64_t DriftingClock::TimeInMicroseconds() {
-  return clock_->TimeInMicroseconds() + Drift();
+Timestamp DriftingClock::CurrentTime() {
+  return clock_->CurrentTime() + Drift() / 1000.;
 }
 
 NtpTime DriftingClock::CurrentNtpTime() {
@@ -45,12 +39,12 @@ NtpTime DriftingClock::CurrentNtpTime() {
 
   NtpTime ntp = clock_->CurrentNtpTime();
   uint64_t total_fractions = static_cast<uint64_t>(ntp);
-  total_fractions += Drift() * kNtpFracPerMicroSecond;
+  total_fractions += Drift().us() * kNtpFracPerMicroSecond;
   return NtpTime(total_fractions);
 }
 
 int64_t DriftingClock::CurrentNtpInMilliseconds() {
-  return clock_->CurrentNtpInMilliseconds() + Drift() / 1000.;
+  return clock_->CurrentNtpInMilliseconds() + Drift().ms();
 }
 }  // namespace test
 }  // namespace webrtc
diff --git a/test/drifting_clock.h b/test/drifting_clock.h
index 46e3c1b7a5..9ed3923588 100644
--- a/test/drifting_clock.h
+++ b/test/drifting_clock.h
@@ -30,17 +30,16 @@ class DriftingClock : public Clock {
   static float PercentsFaster(float percent) { return 1.0f + percent / 100.0f; }
   static float PercentsSlower(float percent) { return 1.0f - percent / 100.0f; }
 
-  int64_t TimeInMilliseconds() override;
-  int64_t TimeInMicroseconds() override;
+  Timestamp CurrentTime() override;
   NtpTime CurrentNtpTime() override;
   int64_t CurrentNtpInMilliseconds() override;
 
  private:
-  float Drift() const;
+  TimeDelta Drift() const;
 
   Clock* const clock_;
   const float drift_;
-  const int64_t start_time_;
+  const Timestamp start_time_;
 };
 }  // namespace test
 }  // namespace webrtc