diff --git a/BUILD b/BUILD
index b49983d16a5..2f9d5a44661 100644
--- a/BUILD
+++ b/BUILD
@@ -1687,6 +1687,9 @@ grpc_cc_library(
     hdrs = [
         "src/core/lib/gprpp/time.h",
     ],
+    external_deps = [
+        "absl/strings:str_format",
+    ],
     deps = [
         "gpr",
         "gpr_codegen",
diff --git a/src/core/ext/filters/client_channel/resolver/xds/xds_resolver.cc b/src/core/ext/filters/client_channel/resolver/xds/xds_resolver.cc
index 5c3e0ef1c34..738f22cf031 100644
--- a/src/core/ext/filters/client_channel/resolver/xds/xds_resolver.cc
+++ b/src/core/ext/filters/client_channel/resolver/xds/xds_resolver.cc
@@ -497,18 +497,15 @@ grpc_error_handle XdsResolver::XdsConfigSelector::CreateMethodConfig(
   if (route_action.retry_policy.has_value() &&
       !route_action.retry_policy->retry_on.Empty()) {
     std::vector<std::string> retry_parts;
-    const auto base_interval =
-        route_action.retry_policy->retry_back_off.base_interval.as_timespec();
-    const auto max_interval =
-        route_action.retry_policy->retry_back_off.max_interval.as_timespec();
     retry_parts.push_back(absl::StrFormat(
         "\"retryPolicy\": {\n"
         "      \"maxAttempts\": %d,\n"
-        "      \"initialBackoff\": \"%d.%09ds\",\n"
-        "      \"maxBackoff\": \"%d.%09ds\",\n"
+        "      \"initialBackoff\": \"%s\",\n"
+        "      \"maxBackoff\": \"%s\",\n"
         "      \"backoffMultiplier\": 2,\n",
-        route_action.retry_policy->num_retries + 1, base_interval.tv_sec,
-        base_interval.tv_nsec, max_interval.tv_sec, max_interval.tv_nsec));
+        route_action.retry_policy->num_retries + 1,
+        route_action.retry_policy->retry_back_off.base_interval.ToJsonString(),
+        route_action.retry_policy->retry_back_off.max_interval.ToJsonString()));
     std::vector<std::string> code_parts;
     if (route_action.retry_policy->retry_on.Contains(GRPC_STATUS_CANCELLED)) {
       code_parts.push_back("        \"CANCELLED\"");
@@ -536,9 +533,9 @@ grpc_error_handle XdsResolver::XdsConfigSelector::CreateMethodConfig(
   // Set timeout.
   if (route_action.max_stream_duration.has_value() &&
       (route_action.max_stream_duration != Duration::Zero())) {
-    gpr_timespec ts = route_action.max_stream_duration->as_timespec();
-    fields.emplace_back(absl::StrFormat("    \"timeout\": \"%d.%09ds\"",
-                                        ts.tv_sec, ts.tv_nsec));
+    fields.emplace_back(
+        absl::StrFormat("    \"timeout\": \"%s\"",
+                        route_action.max_stream_duration->ToJsonString()));
   }
   // Handle xDS HTTP filters.
   XdsRouting::GeneratePerHttpFilterConfigsResult result =
diff --git a/src/core/ext/xds/xds_http_fault_filter.cc b/src/core/ext/xds/xds_http_fault_filter.cc
index 015556faaec..c257c0a7fc1 100644
--- a/src/core/ext/xds/xds_http_fault_filter.cc
+++ b/src/core/ext/xds/xds_http_fault_filter.cc
@@ -36,6 +36,7 @@
 #include <grpc/grpc.h>
 
 #include "src/core/ext/filters/fault_injection/fault_injection_filter.h"
+#include "src/core/ext/xds/xds_common_types.h"
 #include "src/core/ext/xds/xds_http_filters.h"
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/channel/channel_stack.h"
@@ -140,9 +141,8 @@ absl::StatusOr<Json> ParseHttpFaultIntoJson(
         envoy_extensions_filters_common_fault_v3_FaultDelay_fixed_delay(
             fault_delay);
     if (delay_duration != nullptr) {
-      fault_injection_policy_json["delay"] = absl::StrFormat(
-          "%d.%09ds", google_protobuf_Duration_seconds(delay_duration),
-          google_protobuf_Duration_nanos(delay_duration));
+      fault_injection_policy_json["delay"] =
+          ParseDuration(delay_duration).ToJsonString();
     }
     // Set the headers if we enabled header delay injection control
     if (envoy_extensions_filters_common_fault_v3_FaultDelay_has_header_delay(
diff --git a/src/core/lib/gprpp/time.cc b/src/core/lib/gprpp/time.cc
index c7f02d5c2f9..00973b3f89c 100644
--- a/src/core/lib/gprpp/time.cc
+++ b/src/core/lib/gprpp/time.cc
@@ -21,6 +21,8 @@
 #include <limits>
 #include <string>
 
+#include "absl/strings/str_format.h"
+
 #include <grpc/impl/codegen/gpr_types.h>
 #include <grpc/support/log.h>
 
@@ -182,6 +184,11 @@ std::string Duration::ToString() const {
   return std::to_string(millis_) + "ms";
 }
 
+std::string Duration::ToJsonString() const {
+  gpr_timespec ts = as_timespec();
+  return absl::StrFormat("%d.%09ds", ts.tv_sec, ts.tv_nsec);
+}
+
 void TestOnlySetProcessEpoch(gpr_timespec epoch) {
   g_process_epoch_seconds.store(
       gpr_convert_clock_type(epoch, GPR_CLOCK_MONOTONIC).tv_sec);
diff --git a/src/core/lib/gprpp/time.h b/src/core/lib/gprpp/time.h
index d4eacc14f69..3b695389734 100644
--- a/src/core/lib/gprpp/time.h
+++ b/src/core/lib/gprpp/time.h
@@ -211,6 +211,11 @@ class Duration {
 
   std::string ToString() const;
 
+  // Returns the duration in the JSON form corresponding to a
+  // google.protobuf.Duration proto, as defined here:
+  // https://developers.google.com/protocol-buffers/docs/proto3#json
+  std::string ToJsonString() const;
+
  private:
   explicit constexpr Duration(int64_t millis) : millis_(millis) {}