diff --git a/include/takatori/datetime/conversion.h b/include/takatori/datetime/conversion.h
index ec3d08e..12c1cd4 100644
--- a/include/takatori/datetime/conversion.h
+++ b/include/takatori/datetime/conversion.h
@@ -1,7 +1,7 @@
 #pragma once
 
 #include <optional>
-#include <string>
+#include <string_view>
 
 #include <takatori/util/either.h>
 
@@ -23,7 +23,7 @@ using conversion_result = util::either<std::string, T>;
  * @return the parsed date information
  * @return an error message if the conversion was failed
  */
-[[nodiscard]] conversion_result<date_info> parse_date(std::string const& contents);
+[[nodiscard]] conversion_result<date_info> parse_date(std::string_view contents);
 
 /**
  * @brief parses the given contents as a time of day.
@@ -32,7 +32,7 @@ using conversion_result = util::either<std::string, T>;
  * @return the parsed time of day information
  * @return an error message if the conversion was failed
  */
-[[nodiscard]] conversion_result<time_info> parse_time(std::string const& contents);
+[[nodiscard]] conversion_result<time_info> parse_time(std::string_view contents);
 
 /**
  * @brief parses the given contents as a datetime, with or without zone offset.
@@ -41,7 +41,7 @@ using conversion_result = util::either<std::string, T>;
  * @return the parsed datetime information with or without zone offset
  * @return an error message if the conversion was failed
  */
-[[nodiscard]] conversion_result<datetime_info> parse_datetime(std::string const& contents);
+[[nodiscard]] conversion_result<datetime_info> parse_datetime(std::string_view contents);
 
 /**
  * @brief parses the given contents as a zone offset.
@@ -50,6 +50,6 @@ using conversion_result = util::either<std::string, T>;
  * @return the parsed zone offset
  * @return an error message if the conversion was failed
  */
-[[nodiscard]] conversion_result<zone_offset_info> parse_zone_offset(std::string const& contents);
+[[nodiscard]] conversion_result<zone_offset_info> parse_zone_offset(std::string_view contents);
 
 } // namespace takatori::datetime
diff --git a/src/takatori/datetime/conversion.cpp b/src/takatori/datetime/conversion.cpp
index d1098f7..f18e8f6 100644
--- a/src/takatori/datetime/conversion.cpp
+++ b/src/takatori/datetime/conversion.cpp
@@ -72,7 +72,7 @@ std::optional<std::string> require_offset(std::optional<zone_offset_info> const&
 
 } // namespace
 
-conversion_result<date_info> parse_date(std::string const& contents) {
+conversion_result<date_info> parse_date(std::string_view contents) {
     parser::parser p {};
     auto result = p(contents);
     if (!result) {
@@ -91,7 +91,7 @@ conversion_result<date_info> parse_date(std::string const& contents) {
     return *info.date;
 }
 
-conversion_result<time_info> parse_time(std::string const& contents) {
+conversion_result<time_info> parse_time(std::string_view contents) {
     parser::parser p {};
     auto result = p(contents);
     if (!result) {
@@ -110,7 +110,7 @@ conversion_result<time_info> parse_time(std::string const& contents) {
     return *info.time;
 }
 
-conversion_result<datetime_info> parse_datetime(std::string const& contents) {
+conversion_result<datetime_info> parse_datetime(std::string_view contents) {
     parser::parser p {};
     auto result = p(contents);
     if (!result) {
@@ -136,7 +136,7 @@ conversion_result<datetime_info> parse_datetime(std::string const& contents) {
     return datetime_info { *info.date, *info.time, info.offset };
 }
 
-conversion_result<zone_offset_info> parse_zone_offset(std::string const& contents) {
+conversion_result<zone_offset_info> parse_zone_offset(std::string_view contents) {
     parser::parser p {};
     auto result = p(contents);
     if (!result) {
diff --git a/src/takatori/datetime/parser/parser.cpp b/src/takatori/datetime/parser/parser.cpp
index 7e77fae..5b76217 100644
--- a/src/takatori/datetime/parser/parser.cpp
+++ b/src/takatori/datetime/parser/parser.cpp
@@ -13,9 +13,9 @@ parser &parser::set_debug(int level) noexcept {
     return *this;
 }
 
-parser::result_type parser::operator()(std::string const& contents) const {
+parser::result_type parser::operator()(std::string_view contents) const {
     std::istringstream input {
-            contents,
+            std::string { contents },
     };
     driver driver {};
     scanner scanner { input };
@@ -30,7 +30,7 @@ parser::result_type parser::operator()(std::string const& contents) const {
     return std::move(driver.result());
 }
 
-parser::result_type parse(std::string const& contents, parser const& engine) {
+parser::result_type parse(std::string_view contents, parser const& engine) {
     return engine(contents);
 }
 
diff --git a/src/takatori/datetime/parser/parser.h b/src/takatori/datetime/parser/parser.h
index 84df9a6..a68218b 100644
--- a/src/takatori/datetime/parser/parser.h
+++ b/src/takatori/datetime/parser/parser.h
@@ -1,7 +1,7 @@
 #pragma once
 
 #include <optional>
-#include <string>
+#include <string_view>
 #include <variant>
 
 #include <takatori/util/either.h>
@@ -19,12 +19,12 @@ class parser {
 
     parser& set_debug(int level = 1) noexcept;
 
-    [[nodiscard]] result_type operator()(std::string const& contents) const;
+    [[nodiscard]] result_type operator()(std::string_view contents) const;
 
 private:
     int debug_ {};
 };
 
-parser::result_type parse(std::string const& contents, parser const& engine = {});
+parser::result_type parse(std::string_view contents, parser const& engine = {});
 
 } // namespace takatori::datetime::parser