diff --git a/composer.json b/composer.json
index 22900f0..fc7fbd3 100644
--- a/composer.json
+++ b/composer.json
@@ -12,7 +12,8 @@
     "minimum-stability": "dev",
     "require": {
       "ext-json": "*",
-      "ext-openssl": "*"
+      "ext-openssl": "*",
+      "ext-bcmath": "*"
     },
     "autoload": {
         "psr-4": {
diff --git a/src/siam/DateTool.php b/src/siam/DateTool.php
new file mode 100644
index 0000000..35bfdfc
--- /dev/null
+++ b/src/siam/DateTool.php
@@ -0,0 +1,65 @@
+<?php
+
+namespace Siam;
+
+
+class DateTool
+{
+
+    /**
+     * 两个日期跨越的区间
+     * @param $start
+     * @param $end
+     * @return string|null
+     */
+    public static function dateSection($start, $end)
+    {
+        $diff = strtotime($start) - strtotime($end);
+
+        $diffHour = bcdiv($diff, 60 * 60, 2); // 差距的小时
+        $diffDay  = bcdiv($diffHour,24,2); // 差距的天数
+
+        return abs($diffDay);
+    }
+
+    /* **********************
+
+    取日期 测试案例
+
+    $first = DateTool::getMonthFirst(time());
+    $end   = DateTool::getMonthEnd($first);
+
+    dump($first);
+    halt($end);
+
+    ********************** */
+
+    /**
+     * 获取时间当月的第一天日期 默认本月
+     * @param $time
+     * @param string $format
+     * @return bool|false|string
+     */
+    public static function getMonthFirst($time = null, $format = 'Y-m-01')
+    {
+        if ($time === null){
+            $time = time();
+        }
+
+        if (!is_numeric($time)){
+            return false;
+        }
+        return date($format, $time);
+    }
+
+    /**
+     * 获取月份最后一天的日期
+     * @param $first
+     * @param string $format
+     * @return false|string
+     */
+    public static function getMonthEnd($first, $format = 'Y-m-d')
+    {
+        return date($format, strtotime("{$first} +1 month -1 day"));
+    }
+}
\ No newline at end of file