diff --git a/external_parser/event_processors/loop.h b/external_parser/event_processors/loop.h
index 3f0cb80c0..7a3ef2e54 100644
--- a/external_parser/event_processors/loop.h
+++ b/external_parser/event_processors/loop.h
@@ -37,9 +37,10 @@ struct loop_info {
   sticky_value<float> default_reward = sticky_value<float>(0.f);
   sticky_value<v2::LearningModeType> learning_mode_config = sticky_value<v2::LearningModeType>(v2::LearningModeType_Online);
   sticky_value<v2::ProblemType> problem_type_config;
+  sticky_value<bool> use_client_time = sticky_value<bool>(false);
 
   bool is_configured() const {
-    return default_reward.is_valid()  && learning_mode_config.is_valid() && problem_type_config.is_valid();
+    return default_reward.is_valid()  && learning_mode_config.is_valid() && problem_type_config.is_valid() && use_client_time.is_valid();
   }//&& type.is_valid()
 };
 } // namespace loop
\ No newline at end of file
diff --git a/external_parser/event_processors/metadata.h b/external_parser/event_processors/metadata.h
index 05530fdf4..1de047295 100644
--- a/external_parser/event_processors/metadata.h
+++ b/external_parser/event_processors/metadata.h
@@ -10,7 +10,6 @@ namespace v2 = reinforcement_learning::messages::flatbuff::v2;
 namespace metadata {
 // used both for interactions and observations
 struct event_metadata_info {
-  TimePoint client_time_utc;
   std::string app_id;
   v2::PayloadType payload_type;
   float pass_probability;
diff --git a/external_parser/event_processors/timestamp_helper.cc b/external_parser/event_processors/timestamp_helper.cc
index 482be3946..4ee3b224e 100644
--- a/external_parser/event_processors/timestamp_helper.cc
+++ b/external_parser/event_processors/timestamp_helper.cc
@@ -1,4 +1,5 @@
 #include "timestamp_helper.h"
+#include "io/logger.h"
 
 TimePoint timestamp_to_chrono(const v2::TimeStamp &ts) {
 
@@ -14,4 +15,24 @@ TimePoint timestamp_to_chrono(const v2::TimeStamp &ts) {
                         date::day(ts.day())) +
          std::chrono::hours(ts.hour()) + std::chrono::minutes(ts.minute()) +
          std::chrono::seconds(ts.second());
+}
+
+bool is_empty_timestamp(const v2::TimeStamp &ts) {
+  return (ts.year() == 0 && ts.month() == 0 && ts.day() == 0 &&
+          ts.hour() == 0 && ts.minute() == 0 && ts.second() == 0);
+}
+
+TimePoint get_enqueued_time(const v2::TimeStamp *enqueued_time_utc,
+                            const v2::TimeStamp *client_time_utc,
+                            bool use_client_time) {
+  if (use_client_time) {
+    if (!client_time_utc || is_empty_timestamp(*client_time_utc)) {
+      VW::io::logger::log_warn(
+          "binary parser is configured to use client-provided EnqueuedTimeUTC, "
+          "but input metadata does not contain a client timestamp.");
+      return timestamp_to_chrono(*enqueued_time_utc);
+    }
+    return timestamp_to_chrono(*client_time_utc);
+  }
+  return timestamp_to_chrono(*enqueued_time_utc);
 }
\ No newline at end of file
diff --git a/external_parser/event_processors/timestamp_helper.h b/external_parser/event_processors/timestamp_helper.h
index 88ecbebb3..ac85784c7 100644
--- a/external_parser/event_processors/timestamp_helper.h
+++ b/external_parser/event_processors/timestamp_helper.h
@@ -7,4 +7,8 @@
 
 namespace v2 = reinforcement_learning::messages::flatbuff::v2;
 using TimePoint = std::chrono::time_point<std::chrono::system_clock>;
-TimePoint timestamp_to_chrono(const v2::TimeStamp &ts);
\ No newline at end of file
+TimePoint timestamp_to_chrono(const v2::TimeStamp &ts);
+bool is_empty_timestamp(const v2::TimeStamp &ts);
+TimePoint get_enqueued_time(const v2::TimeStamp *enqueued_time_utc,
+                            const v2::TimeStamp *client_time_utc,
+                            bool use_client_time);
\ No newline at end of file
diff --git a/external_parser/event_processors/typed_events.h b/external_parser/event_processors/typed_events.h
index a46ca4924..8ed8160d0 100644
--- a/external_parser/event_processors/typed_events.h
+++ b/external_parser/event_processors/typed_events.h
@@ -81,10 +81,7 @@ template <> struct event_processor<v2::MultiSlotEvent> {
     ccb_data->probability_of_drop = 1.f - metadata.pass_probability();
 
     return {TimePoint(enqueued_time_utc),
-            {metadata.client_time_utc()
-                 ? timestamp_to_chrono(*metadata.client_time_utc())
-                 : TimePoint(),
-             metadata.app_id() ? metadata.app_id()->str() : "",
+            {metadata.app_id() ? metadata.app_id()->str() : "",
              metadata.payload_type(), metadata.pass_probability(),
              metadata.encoding(), metadata.id()->str(), evt.learning_mode()},
             std::move(line_vec),
@@ -147,10 +144,7 @@ template <> struct event_processor<v2::CbEvent> {
     cb_data->interaction_data.skipLearn = evt.deferred_action();
 
     return {TimePoint(enqueued_time_utc),
-            {metadata.client_time_utc()
-                 ? timestamp_to_chrono(*metadata.client_time_utc())
-                 : TimePoint(),
-             metadata.app_id() ? metadata.app_id()->str() : "",
+            {metadata.app_id() ? metadata.app_id()->str() : "",
              metadata.payload_type(), metadata.pass_probability(),
              metadata.encoding(), metadata.id()->str(), evt.learning_mode()},
             std::move(line_vec),
@@ -201,10 +195,7 @@ template <> struct event_processor<v2::CaEvent> {
     ca_data->interaction_data.skipLearn = evt.deferred_action();
 
     return {TimePoint(enqueued_time_utc),
-            {metadata.client_time_utc()
-                 ? timestamp_to_chrono(*metadata.client_time_utc())
-                 : TimePoint(),
-             metadata.app_id() ? metadata.app_id()->str() : "",
+            {metadata.app_id() ? metadata.app_id()->str() : "",
              metadata.payload_type(), metadata.pass_probability(),
              metadata.encoding(), metadata.id()->str(), evt.learning_mode()},
             std::move(line_vec),
diff --git a/external_parser/joiners/example_joiner.cc b/external_parser/joiners/example_joiner.cc
index a7e465e40..04567d209 100644
--- a/external_parser/joiners/example_joiner.cc
+++ b/external_parser/joiners/example_joiner.cc
@@ -116,6 +116,10 @@ void example_joiner::set_problem_type_config(v2::ProblemType problem_type,
   _loop_info.problem_type_config.set(problem_type, sticky);
 }
 
+void example_joiner::set_use_client_time(bool use_client_time, bool sticky) {
+  _loop_info.use_client_time.set(use_client_time, sticky);
+}
+
 bool example_joiner::joiner_ready() {
   return _loop_info.is_configured() && _reward_calculation.is_valid();
 }
@@ -223,10 +227,9 @@ bool example_joiner::process_interaction(const v2::Event &event,
       return false;
     }
 
-    je = std::move(
-        typed_event::event_processor<v2::CbEvent>::fill_in_joined_event(
-            *cb, metadata, enqueued_time_utc,
-            typed_event::event_processor<v2::CbEvent>::get_context(*cb)));
+    je = typed_event::event_processor<v2::CbEvent>::fill_in_joined_event(
+        *cb, metadata, enqueued_time_utc,
+        typed_event::event_processor<v2::CbEvent>::get_context(*cb));
   } else if (metadata.payload_type() == v2::PayloadType_CCB) {
     const v2::MultiSlotEvent *ccb = nullptr;
     if (!typed_event::process_compression<v2::MultiSlotEvent>(
@@ -243,11 +246,9 @@ bool example_joiner::process_interaction(const v2::Event &event,
                                metadata.id()->c_str());
       return false;
     }
-    je = std::move(
-        typed_event::event_processor<v2::MultiSlotEvent>::fill_in_joined_event(
-            *ccb, metadata, enqueued_time_utc,
-            typed_event::event_processor<v2::MultiSlotEvent>::get_context(
-                *ccb)));
+    je = typed_event::event_processor<v2::MultiSlotEvent>::fill_in_joined_event(
+        *ccb, metadata, enqueued_time_utc,
+        typed_event::event_processor<v2::MultiSlotEvent>::get_context(*ccb));
   } else if (metadata.payload_type() == v2::PayloadType_CA) {
     const v2::CaEvent *ca = nullptr;
     if (!typed_event::process_compression<v2::CaEvent>(
@@ -263,10 +264,9 @@ bool example_joiner::process_interaction(const v2::Event &event,
                                metadata.id()->c_str());
       return false;
     }
-    je = std::move(
-        typed_event::event_processor<v2::CaEvent>::fill_in_joined_event(
-            *ca, metadata, enqueued_time_utc,
-            typed_event::event_processor<v2::CaEvent>::get_context(*ca)));
+    je = typed_event::event_processor<v2::CaEvent>::fill_in_joined_event(
+        *ca, metadata, enqueued_time_utc,
+        typed_event::event_processor<v2::CaEvent>::get_context(*ca));
   } else {
     // for now only CB is supported so log and return false
     VW::io::logger::log_error("Interaction event learning mode [{}] not "
@@ -276,19 +276,19 @@ bool example_joiner::process_interaction(const v2::Event &event,
     return false;
   }
 
-  if(!_binary_to_json) {
+  if (!_binary_to_json) {
     std::string context(je.context);
     try {
       if (_vw->audit || _vw->hash_inv) {
         VW::template read_line_json<true>(
             *_vw, examples, const_cast<char *>(context.c_str()),
-            reinterpret_cast<VW::example_factory_t>(&VW::get_unused_example), _vw,
-            &_dedup_cache.dedup_examples);
+            reinterpret_cast<VW::example_factory_t>(&VW::get_unused_example),
+            _vw, &_dedup_cache.dedup_examples);
       } else {
         VW::template read_line_json<false>(
             *_vw, examples, const_cast<char *>(context.c_str()),
-            reinterpret_cast<VW::example_factory_t>(&VW::get_unused_example), _vw,
-            &_dedup_cache.dedup_examples);
+            reinterpret_cast<VW::example_factory_t>(&VW::get_unused_example),
+            _vw, &_dedup_cache.dedup_examples);
       }
     } catch (VW::vw_exception &e) {
       VW::io::logger::log_warn(
@@ -309,15 +309,13 @@ bool example_joiner::process_outcome(const v2::Event &event,
                                      const v2::Metadata &metadata,
                                      const TimePoint &enqueued_time_utc) {
   reward::outcome_event o_event;
-  o_event.metadata = {metadata.client_time_utc()
-                          ? timestamp_to_chrono(*metadata.client_time_utc())
-                          : TimePoint(),
-                      metadata.app_id() ? metadata.app_id()->str() : "",
+  o_event.metadata = {metadata.app_id() ? metadata.app_id()->str() : "",
                       metadata.payload_type(),
                       metadata.pass_probability(),
                       metadata.encoding(),
                       metadata.id()->str(),
-                      v2::LearningModeType_Online }; //Online is the default value, we should not leave this uninitialized
+                      v2::LearningModeType_Online};
+
   o_event.enqueued_time_utc = enqueued_time_utc;
 
   const v2::OutcomeEvent *outcome = nullptr;
@@ -428,7 +426,9 @@ bool example_joiner::process_joined(v_array<example *> &examples) {
   for (auto &joined_event : _batch_grouped_events[id]) {
     auto event = flatbuffers::GetRoot<v2::Event>(joined_event->event()->data());
     auto metadata = event->meta();
-    auto enqueued_time_utc = timestamp_to_chrono(*joined_event->timestamp());
+    auto enqueued_time_utc = get_enqueued_time(joined_event->timestamp(),
+                                               metadata->client_time_utc(),
+                                               _loop_info.use_client_time);
     const auto &payload_type = metadata->payload_type();
 
     if (payload_type == v2::PayloadType_Outcome) {
@@ -454,8 +454,6 @@ bool example_joiner::process_joined(v_array<example *> &examples) {
         if (!je->is_joined_event_learnable()) {
           _joiner_metrics.number_of_skipped_events++;
         } else {
-          // TODO does this potentially need to check and set client time utc if
-          // that option is on?
           if (_joiner_metrics.first_event_id.empty()) {
             _joiner_metrics.first_event_id =
                 std::move(je->interaction_metadata.event_id);
@@ -520,7 +518,6 @@ bool example_joiner::process_joined(v_array<example *> &examples) {
   }
   je->set_reward_from_data(examples);
 
-
   if (multiline) {
     // add an empty example to signal end-of-multiline
     examples.push_back(&VW::get_unused_example(_vw));
diff --git a/external_parser/joiners/example_joiner.h b/external_parser/joiners/example_joiner.h
index b4a705e90..132c6a7f2 100644
--- a/external_parser/joiners/example_joiner.h
+++ b/external_parser/joiners/example_joiner.h
@@ -26,11 +26,13 @@ class example_joiner : public i_joiner {
   void set_default_reward(float default_reward, bool sticky = false) override;
   void set_learning_mode_config(v2::LearningModeType learning_mode, bool sticky = false) override;
   void set_problem_type_config(v2::ProblemType problem_type, bool sticky = false) override;
+  void set_use_client_time(bool use_client_time, bool sticky = false) override;
   bool joiner_ready() override;
 
   float default_reward() const { return _loop_info.default_reward; }
   v2::LearningModeType learning_mode_config() const { return _loop_info.learning_mode_config; }
   v2::ProblemType problem_type_config() const { return _loop_info.problem_type_config; }
+  bool use_client_time() const { return _loop_info.use_client_time; }
 
   // Takes an event which will have a timestamp and event payload
   // groups all events interactions with their event observations based on their
diff --git a/external_parser/joiners/i_joiner.h b/external_parser/joiners/i_joiner.h
index f0b4e0345..63b4ffe8e 100644
--- a/external_parser/joiners/i_joiner.h
+++ b/external_parser/joiners/i_joiner.h
@@ -31,6 +31,7 @@ class i_joiner {
   virtual void set_default_reward(float default_reward, bool sticky = false) = 0;
   virtual void set_learning_mode_config(v2::LearningModeType learning_mode, bool sticky = false) = 0;
   virtual void set_problem_type_config(v2::ProblemType problem_type, bool sticky = false) = 0;
+  virtual void set_use_client_time(bool use_client_time, bool sticky = false) = 0;
 
   /**
    * @brief Tells whether config was provided such that it can start joining examples.
diff --git a/external_parser/joiners/multistep_example_joiner.cc b/external_parser/joiners/multistep_example_joiner.cc
index b0832d742..6c8973e8c 100644
--- a/external_parser/joiners/multistep_example_joiner.cc
+++ b/external_parser/joiners/multistep_example_joiner.cc
@@ -31,7 +31,9 @@ multistep_example_joiner::~multistep_example_joiner() {
 bool multistep_example_joiner::process_event(const v2::JoinedEvent &joined_event) {
   auto event = flatbuffers::GetRoot<v2::Event>(joined_event.event()->data());
   const v2::Metadata& meta = *event->meta();
-  auto enqueued_time_utc = timestamp_to_chrono(*joined_event.timestamp());
+  auto enqueued_time_utc = get_enqueued_time(joined_event.timestamp(),
+                                               meta.client_time_utc(),
+                                               _loop_info.use_client_time);
   switch (meta.payload_type()) {
     case v2::PayloadType_MultiStep:
     {
@@ -69,6 +71,10 @@ void multistep_example_joiner::set_problem_type_config(v2::ProblemType problem_t
   _loop_info.problem_type_config.set(problem_type, sticky);
 }
 
+void multistep_example_joiner::set_use_client_time(bool use_client_time, bool sticky) {
+  _loop_info.use_client_time.set(use_client_time, sticky);
+}
+
 bool multistep_example_joiner::joiner_ready() {
   return _loop_info.is_configured() && _reward_calculation.is_valid();
 }
@@ -121,8 +127,7 @@ reward::outcome_event multistep_example_joiner::process_outcome(const multistep_
   const auto& metadata = event_meta.meta;
   const auto& event = event_meta.event;
   reward::outcome_event o_event;
-  o_event.metadata = {timestamp_to_chrono(*metadata.client_time_utc()),
-                      metadata.app_id() ? metadata.app_id()->str() : "",
+  o_event.metadata = {metadata.app_id() ? metadata.app_id()->str() : "",
                       metadata.payload_type(),
                       metadata.pass_probability(),
                       metadata.encoding(),
@@ -142,9 +147,7 @@ joined_event::joined_event multistep_example_joiner::process_interaction(
     v_array<example *> &examples) {
   const auto& metadata = event_meta.meta;
   const auto& event = event_meta.event;
-  metadata::event_metadata_info meta = {metadata.client_time_utc()
-                         ? timestamp_to_chrono(*metadata.client_time_utc())
-                         : TimePoint(),
+  metadata::event_metadata_info meta = {
                         metadata.app_id() ? metadata.app_id()->str() : "",
                         metadata.payload_type(),
                         metadata.pass_probability(),
diff --git a/external_parser/joiners/multistep_example_joiner.h b/external_parser/joiners/multistep_example_joiner.h
index adf066182..78bdc2364 100644
--- a/external_parser/joiners/multistep_example_joiner.h
+++ b/external_parser/joiners/multistep_example_joiner.h
@@ -33,6 +33,7 @@ class multistep_example_joiner : public i_joiner {
   void set_default_reward(float default_reward, bool sticky) override;
   void set_learning_mode_config(v2::LearningModeType learning_mode, bool sticky) override;
   void set_problem_type_config(v2::ProblemType problem_type, bool sticky) override;
+  void set_use_client_time(bool use_client_time, bool sticky = false) override;
   bool joiner_ready() override;
 
   bool current_event_is_skip_learn() override;
diff --git a/external_parser/parse_example_binary.cc b/external_parser/parse_example_binary.cc
index 307b457c9..71b27fa96 100644
--- a/external_parser/parse_example_binary.cc
+++ b/external_parser/parse_example_binary.cc
@@ -195,6 +195,7 @@ bool binary_parser::read_checkpoint_msg(io_buf *input) {
       checkpoint_info->learning_mode_config());
   _example_joiner->set_problem_type_config(
       checkpoint_info->problem_type_config());
+  _example_joiner->set_use_client_time(checkpoint_info->use_client_time());
 
   return true;
 }
diff --git a/external_parser/parse_example_external.cc b/external_parser/parse_example_external.cc
index ca9c24147..40516831f 100644
--- a/external_parser/parse_example_external.cc
+++ b/external_parser/parse_example_external.cc
@@ -89,6 +89,9 @@ void apply_cli_overrides(std::unique_ptr<i_joiner>& joiner, vw *all, const input
     }
     joiner->set_problem_type_config(problem_type, true);
   }
+  if(all->options->was_supplied("use_client_time")) {
+    joiner->set_use_client_time(parsed_options.ext_opts->use_client_time, true);
+  }
   if(all->options->was_supplied("learning_mode")) {
     v2::LearningModeType learning_mode;
     if(!str_to_learning_mode(parsed_options.ext_opts->learning_mode, learning_mode)) {
@@ -167,6 +170,9 @@ void parser::set_parse_args(VW::config::option_group_definition &in_options,
     .add(
       VW::config::make_option("problem_type", parsed_options.ext_opts->problem_type)
         .help("Override the problem type trying to be solved, valid values: CB, CCB, SLATES, CA"))
+    .add(
+      VW::config::make_option("use_client_time", parsed_options.ext_opts->use_client_time)
+        .help("Override use_client_time to define whether client time or enqueued time will be used for reward calculation"))
     .add(
       VW::config::make_option("reward_function", parsed_options.ext_opts->reward_function)
         .help("Override the reward function to be used, valid values: earliest, average, median, sum, min, max"))
diff --git a/external_parser/parse_example_external.h b/external_parser/parse_example_external.h
index 5777fe098..3202d27ed 100644
--- a/external_parser/parse_example_external.h
+++ b/external_parser/parse_example_external.h
@@ -19,6 +19,7 @@ struct parser_options {
   std::string problem_type;
   std::string reward_function;
   std::string learning_mode;
+  bool use_client_time;
 };
 
 int parse_examples(vw *all, v_array<example *> &examples);
diff --git a/external_parser/unit_tests/CMakeLists.txt b/external_parser/unit_tests/CMakeLists.txt
index 5430e4160..b2c573489 100644
--- a/external_parser/unit_tests/CMakeLists.txt
+++ b/external_parser/unit_tests/CMakeLists.txt
@@ -13,6 +13,7 @@ set(TEST_SOURCES
   test_log_converter.cc
   test_skip_learn.cc
   test_metrics.cc
+  test_client_and_enqueued_time.cc
 )
 
 add_executable(binary_parser_unit_tests ${TEST_SOURCES})
diff --git a/external_parser/unit_tests/test_client_and_enqueued_time.cc b/external_parser/unit_tests/test_client_and_enqueued_time.cc
new file mode 100644
index 000000000..e9a9160fb
--- /dev/null
+++ b/external_parser/unit_tests/test_client_and_enqueued_time.cc
@@ -0,0 +1,121 @@
+#include "joiners/example_joiner.h"
+#include "test_common.h"
+#include <boost/test/unit_test.hpp>
+
+void process(vw *vw, example_joiner &joiner, v_array<example *> &examples,
+             std::string int_file, std::string obs_file) {
+  std::string input_files = get_test_files_location();
+
+  auto interaction_buffer = read_file(input_files + int_file);
+  // need to keep the fb buffer around in order to process the event
+  std::vector<flatbuffers::DetachedBuffer> int_detached_buffers;
+
+  auto joined_cb_events =
+      wrap_into_joined_events(interaction_buffer, int_detached_buffers);
+
+  for (auto &je : joined_cb_events) {
+    joiner.process_event(*je);
+    examples.push_back(&VW::get_unused_example(vw));
+  }
+
+  // need to keep the fb buffer around in order to process the event
+  std::vector<flatbuffers::DetachedBuffer> obs_detached_buffers;
+
+  auto observation_buffer = read_file(input_files + obs_file);
+  joined_cb_events =
+      wrap_into_joined_events(observation_buffer, obs_detached_buffers);
+
+  for (auto &je : joined_cb_events) {
+    joiner.process_event(*je);
+  }
+
+  BOOST_CHECK_EQUAL(joiner.processing_batch(), true);
+
+  joiner.process_joined(examples);
+}
+
+BOOST_AUTO_TEST_CASE(test_use_client_time_missing_and_configured_to_true) {
+  auto vw = VW::initialize("--quiet --binary_parser --cb_explore_adf", nullptr,
+                           false, nullptr, nullptr);
+
+  example_joiner joiner(vw);
+  v_array<example *> examples;
+
+  joiner.set_problem_type_config(v2::ProblemType_CB);
+  // the test files used do not have a client time utc set, so they will use the
+  // enqueued time utc even though this is set to true
+  joiner.set_use_client_time(true);
+
+  // rewards are {5, 4, 3}
+  // enqueued time goes from latest to earliest
+  // client time goes from earliest to latest
+  float earliest_enqueued = -3.f;
+  process(vw, joiner, examples, "/reward_functions/cb/cb_v2.fb",
+          "/reward_functions/cb/f-reward_3obs_v2.fb");
+
+  BOOST_CHECK_EQUAL(examples[1]->l.cb.costs[0].action, 1);
+  BOOST_CHECK_EQUAL(examples[1]->l.cb.costs[0].cost, earliest_enqueued);
+  BOOST_CHECK_CLOSE(examples[1]->l.cb.costs[0].probability, 0.9, FLOAT_TOL);
+  BOOST_CHECK_EQUAL(examples[1]->l.cb.weight, 1.0f);
+
+  clear_examples(examples, vw);
+  VW::finish(*vw);
+}
+
+BOOST_AUTO_TEST_CASE(test_use_client_time_existing_and_configured_to_false) {
+  auto vw = VW::initialize("--quiet --binary_parser --cb_explore_adf", nullptr,
+                           false, nullptr, nullptr);
+
+  example_joiner joiner(vw);
+  v_array<example *> examples;
+
+  joiner.set_problem_type_config(v2::ProblemType_CB);
+  // the test files used have a client time utc set, but enqueued time will be
+  // used instead
+  joiner.set_use_client_time(false);
+
+  // rewards are {1, 1, 5}
+  // enqueued time goes from latest to earliest
+  // client time goes from earliest to latest
+  float earliest_enqueued = -5.f;
+  float earliest_client = -1.f;
+  process(vw, joiner, examples, "/client_time/cb_v2_client_time.fb",
+          "/client_time/f-reward_3obs_v2_client_time.fb");
+
+  BOOST_CHECK_EQUAL(examples[1]->l.cb.costs[0].action, 1);
+  BOOST_CHECK_EQUAL(examples[1]->l.cb.costs[0].cost, earliest_enqueued);
+  BOOST_CHECK_CLOSE(examples[1]->l.cb.costs[0].probability, 0.9, FLOAT_TOL);
+  BOOST_CHECK_EQUAL(examples[1]->l.cb.weight, 1.0f);
+
+  clear_examples(examples, vw);
+  VW::finish(*vw);
+}
+
+BOOST_AUTO_TEST_CASE(test_use_client_time_existing_and_configured_to_true) {
+  auto vw = VW::initialize("--quiet --binary_parser --cb_explore_adf", nullptr,
+                           false, nullptr, nullptr);
+
+  example_joiner joiner(vw);
+  v_array<example *> examples;
+
+  joiner.set_problem_type_config(v2::ProblemType_CB);
+  // the test files used have a client time set and it should be used instead of
+  // enqueued time utc
+  joiner.set_use_client_time(true);
+
+  // rewards are {1, 1, 5}
+  // enqueued time goes from latest to earliest
+  // client time goes from earliest to latest
+  float earliest_enqueued = -5.f;
+  float earliest_client = -1.f;
+  process(vw, joiner, examples, "/client_time/cb_v2_client_time.fb",
+          "/client_time/f-reward_3obs_v2_client_time.fb");
+
+  BOOST_CHECK_EQUAL(examples[1]->l.cb.costs[0].action, 1);
+  BOOST_CHECK_EQUAL(examples[1]->l.cb.costs[0].cost, earliest_client);
+  BOOST_CHECK_CLOSE(examples[1]->l.cb.costs[0].probability, 0.9, FLOAT_TOL);
+  BOOST_CHECK_EQUAL(examples[1]->l.cb.weight, 1.0f);
+
+  clear_examples(examples, vw);
+  VW::finish(*vw);
+}
\ No newline at end of file
diff --git a/external_parser/unit_tests/test_files/README.md b/external_parser/unit_tests/test_files/README.md
index 6cdbcecbb..6ae5b197a 100644
--- a/external_parser/unit_tests/test_files/README.md
+++ b/external_parser/unit_tests/test_files/README.md
@@ -73,6 +73,15 @@ Residing under `reward_functions`
 - ca_v2.fb: `./example_gen --kind ca --count 1 --seed -1`
 - f-reward_3obs_v2.fb: `./example_gen --kind f-reward --count 3 --seed -1 --random_reward`
 
+### client time utc test files
+
+Residing under `client_time`
+
+Note: these files were generated after setting `"time_provider.implementation"` to `"CLOCK_TIME_PROVIDER"` in the configuration of example_gen
+
+- cb_v2_client_time.fb: `./example_gen --kind cb --count 1 --seed -1`
+- f-reward_3obs_v2_client_time.fb: `./example_gen --kind f-reward --count 3 --seed -1 --random_reward`
+
 ### skip learn test files
 
 Residing under `skip_learn`
diff --git a/external_parser/unit_tests/test_files/client_time/cb_v2_client_time.fb b/external_parser/unit_tests/test_files/client_time/cb_v2_client_time.fb
new file mode 100644
index 000000000..627cb8013
Binary files /dev/null and b/external_parser/unit_tests/test_files/client_time/cb_v2_client_time.fb differ
diff --git a/external_parser/unit_tests/test_files/client_time/f-reward_3obs_v2_client_time.fb b/external_parser/unit_tests/test_files/client_time/f-reward_3obs_v2_client_time.fb
new file mode 100644
index 000000000..912d9d221
Binary files /dev/null and b/external_parser/unit_tests/test_files/client_time/f-reward_3obs_v2_client_time.fb differ
diff --git a/rlclientlib/schema/v2/FileFormat.fbs b/rlclientlib/schema/v2/FileFormat.fbs
index 4c8a39081..622e31884 100644
--- a/rlclientlib/schema/v2/FileFormat.fbs
+++ b/rlclientlib/schema/v2/FileFormat.fbs
@@ -29,6 +29,7 @@ table CheckpointInfo {
     default_reward: float;
     learning_mode_config: LearningModeType;
     problem_type_config: ProblemType;
+    use_client_time: bool;
 }
 
 root_type FileHeader;
diff --git a/test_tools/log_parser/joiner.py b/test_tools/log_parser/joiner.py
index df99c8c0a..c06c9f3f5 100755
--- a/test_tools/log_parser/joiner.py
+++ b/test_tools/log_parser/joiner.py
@@ -72,6 +72,11 @@ def end_vector_shim(builder, len):
     choices=[value for name, value in ProblemType.__dict__.items()],
     help = 'problem type:  0-Unknown, 1-CB, 2-CCB, 3-SLATES, 4-CA'
 )
+arg_parser.add_argument(
+    '--use_client_time',
+    type=bool,
+    help = 'use client time utc when joining/calculating reward, defaults to off'
+)
 arg_parser.add_argument(
     '--observations',
     type=str,
@@ -90,6 +95,7 @@ def end_vector_shim(builder, len):
 arg_parser.add_argument(
     '--verbose',
     type=bool,
+    default=False,
     help = 'verbose output of each message parsed (default to off)'
 )
 
@@ -105,6 +111,7 @@ def end_vector_shim(builder, len):
 observations_file_name = 'observations.fb'
 result_file = 'merged.log'
 verbose = False
+use_client_time = False
 
 
 if args.reward_function:
@@ -131,6 +138,9 @@ def end_vector_shim(builder, len):
 if args.verbose:
     verbose = args.verbose
 
+if args.use_client_time:
+    use_client_time = True
+
 class PreambleStreamReader:
     def __init__(self, file_name):
         self.file = open(file_name, 'rb')
@@ -254,6 +264,7 @@ def write_checkpoint_info(self):
             print("default reward: ", default_reward)
             print("learning_mode_config: ", learning_mode_config)
             print("problem_type_config: ", problem_type_config)
+            print("use_client_time: ", use_client_time)
         builder = flatbuffers.Builder(0)
 
         CheckpointInfoStart(builder)
@@ -261,6 +272,7 @@ def write_checkpoint_info(self):
         CheckpointInfoAddDefaultReward(builder, default_reward)
         CheckpointInfoAddLearningModeConfig(builder, learning_mode_config)
         CheckpointInfoAddProblemTypeConfig(builder, problem_type_config)
+        CheckpointInfoAddUseClientTime(builder, use_client_time)
 
         checkpoint_info_off = CheckpointInfoEnd(builder)
         builder.Finish(checkpoint_info_off)
diff --git a/test_tools/log_parser/log_gen.py b/test_tools/log_parser/log_gen.py
index 9ed41d2ad..e37e175a1 100644
--- a/test_tools/log_parser/log_gen.py
+++ b/test_tools/log_parser/log_gen.py
@@ -98,7 +98,7 @@ def write_regular_message(self, events):
         builder.Finish(joined_payload_off)
         self._write_message(MSG_TYPE_REGULAR, builder.Output())
 
-    def write_checkpoint_info(self, reward_fun = RewardFunctionType.Earliest, default_reward = 0.0, learning_mode = LearningModeType.Online, problem_type = ProblemType.CB):
+    def write_checkpoint_info(self, reward_fun = RewardFunctionType.Earliest, default_reward = 0.0, learning_mode = LearningModeType.Online, problem_type = ProblemType.CB, use_client_time = False):
         builder = flatbuffers.Builder(0)
 
         CheckpointInfoStart(builder)
@@ -106,6 +106,7 @@ def write_checkpoint_info(self, reward_fun = RewardFunctionType.Earliest, defaul
         CheckpointInfoAddDefaultReward(builder, default_reward)
         CheckpointInfoAddLearningModeConfig(builder, learning_mode)
         CheckpointInfoAddProblemTypeConfig(builder, problem_type)
+        CheckpointInfoAddUseClientTime(builder, use_client_time)
 
         checkpoint_info_off = CheckpointInfoEnd(builder)
         builder.Finish(checkpoint_info_off)