diff --git a/examles/sampleCommon.js b/examles/sampleCommon.js
new file mode 100644
index 0000000..98cc6be
--- /dev/null
+++ b/examles/sampleCommon.js
@@ -0,0 +1,4 @@
+const common  = require('../src/lib/common.js');
+
+console.log(common.formatDatetime(new Date(), 'yyyy/MM/dd hh:mm:ss'));
+console.log(common.formatDatetime(new Date(), 'yyyy-MM-ddThh:mm:ss'));
\ No newline at end of file
diff --git a/src/lib/common.js b/src/lib/common.js
index e69de29..bf1fc36 100644
--- a/src/lib/common.js
+++ b/src/lib/common.js
@@ -0,0 +1,22 @@
+const common = {
+    /**
+     * 日時データを指定フォーマットで文字列化する
+     * @param {Date} dt
+     * @param {String} fmt
+     * @returns {String}
+     */
+    formatDatetime(dt,fmt="yyyy-MM-dd hh:mm:ss"){
+        const pad = (n) => n < 10 ? '0' + n : n;
+        const replacements = {
+            "yyyy": dt.getFullYear(),
+            "MM": pad(dt.getMonth() + 1),
+            "dd": pad(dt.getDate()),
+            "hh": pad(dt.getHours()),
+            "mm": pad(dt.getMinutes()),
+            "ss": pad(dt.getSeconds())
+        };
+        return fmt.replace(/yyyy|MM|dd|hh|mm|ss/g, (match) => replacements[match]); 
+    }
+}
+
+module.exports = common;
\ No newline at end of file
diff --git a/tests/test_common.js b/tests/test_common.js
new file mode 100644
index 0000000..e69de29