diff --git a/cyber/time/BUILD b/cyber/time/BUILD
index 2dd264d34384982c01ad34ec96bbe0cdd6fa1ccb..fb276de378e9aedab3269345496749e5358e18f1 100644
--- a/cyber/time/BUILD
+++ b/cyber/time/BUILD
@@ -50,4 +50,18 @@ cc_test(
     ],
 )
 
+cc_library(
+    name = "clock",
+    srcs = ["clock.cc"],
+    hdrs = ["clock.h"],
+    deps = [
+        ":time",
+        "//cyber/common:global_data",
+        "//cyber/common:log",
+        "//cyber/common:macros",
+        "//cyber/common:util",
+        "//cyber/proto:run_mode_conf_cc_proto",
+    ],
+)
+
 cpplint()
diff --git a/cyber/time/clock.cc b/cyber/time/clock.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c0b0670417b81d0af0b15a188ea3856379ba1601
--- /dev/null
+++ b/cyber/time/clock.cc
@@ -0,0 +1,61 @@
+/******************************************************************************
+ * Copyright 2020 The Apollo Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *****************************************************************************/
+
+#include "cyber/time/clock.h"
+
+#include "cyber/common/global_data.h"
+#include "cyber/common/log.h"
+#include "cyber/common/util.h"
+
+namespace apollo {
+namespace cyber {
+
+using GlobalData = ::apollo::cyber::common::GlobalData;
+
+Clock::Clock() {
+    const auto& cyber_config = GlobalData::Instance()->Config();
+    const auto& clock_mode = cyber_config.run_mode_conf().clock_mode();
+    mode_ = clock_mode;
+    mock_now_ = Time(0);
+}
+
+Time Clock::Now() {
+  std::lock_guard<std::mutex> lk(mtx_);
+  switch (mode_) {
+    case ClockMode::MODE_CYBER:
+      return Time::Now();
+    case ClockMode::MODE_MOCK:
+      return mock_now_;
+    default:
+      AFATAL << "Unsupported clock mode: "
+             << apollo::cyber::common::ToInt(mode_);
+  }
+  return Time::Now();
+}
+
+double Clock::NowInSeconds() { return Now().ToSecond(); }
+
+void Clock::SetNow(const Time& now) {
+  std::lock_guard<std::mutex> lk(mtx_);
+  if (mode_ != ClockMode::MODE_MOCK) {
+    AERROR << "SetSimNow only works for ClockMode::MOCK";
+    return;
+  }
+  mock_now_ = now;
+}
+
+}  // namespace cyber
+}  // namespace apollo
diff --git a/cyber/time/clock.h b/cyber/time/clock.h
new file mode 100644
index 0000000000000000000000000000000000000000..22d0ee4659c9defe8527f74a744840d01d69b869
--- /dev/null
+++ b/cyber/time/clock.h
@@ -0,0 +1,83 @@
+/******************************************************************************
+ * Copyright 2020 The Apollo Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *****************************************************************************/
+
+#ifndef CYBER_TIME_CLOCK_H_
+#define CYBER_TIME_CLOCK_H_
+
+#include <mutex>
+
+#include "cyber/common/macros.h"
+#include "cyber/time/time.h"
+#include "cyber/proto/run_mode_conf.pb.h"
+
+namespace apollo {
+namespace cyber {
+
+using ::apollo::cyber::proto::ClockMode;
+
+/**
+ * @class Clock
+ * @brief a singleton clock that can be used to get the current
+ * timestamp. The source can be either system(cyber) clock or a mock clock.
+ * Mock clock is for testing purpose mainly.
+ */
+class Clock {
+ public:
+  static constexpr int64_t PRECISION =
+      std::chrono::system_clock::duration::period::den /
+      std::chrono::system_clock::duration::period::num;
+
+  /// PRECISION >= 1000000 means the precision is at least 1us.
+  static_assert(PRECISION >= 1000000,
+                "The precision of the system clock should be at least 1 "
+                "microsecond.");
+
+  /**
+   * @brief get current time.
+   * @return a Time object representing the current time.
+   */
+  Time Now();
+
+  /**
+   * @brief gets the current time in second.
+   * @return the current time in second.
+   */
+  double NowInSeconds();
+
+  /**
+   * @brief This is for mock clock mode only. It will set the timestamp
+   * for the mock clock.
+   */
+  void SetNow(const Time& now);
+
+  /**
+   * @brief This is for mock clock mode only. It will set the timestamp
+   * for the mock clock with UNIX timestamp in seconds.
+   */
+  void SetNowInSeconds(const double seconds) { SetNow(Time(seconds)); }
+
+ private:
+  ClockMode mode_;
+  Time mock_now_;
+  std::mutex mtx_;
+
+  DECLARE_SINGLETON(Clock)
+};
+
+}  // namespace cyber
+}  // namespace apollo
+
+#endif  // CYBER_TIME_CLOCK_H_