diff --git a/README.md b/README.md
index e4ad94b..84f7b66 100644
--- a/README.md
+++ b/README.md
@@ -736,3 +736,7 @@ Rust标准库`std::collections`提供了4种通用容器类型，包含一下8
 - [参加考试的最大学生数](src/math/maximum_students_taking_exam.rs)  [位运算, 数组, 动态规划, 状态压缩, 矩阵]
 
   - LeetCode 1349. 参加考试的最大学生数 <https://leetcode.cn/problems/maximum-students-taking-exam>
+
+- [一周中的第几天](src/math/day_of_the_week.rs)  [数学]
+
+  - LeetCode 1185. 一周中的第几天 <https://leetcode.cn/problems/day-of-the-week>
diff --git a/images/math/day_of_the_week.jpeg b/images/math/day_of_the_week.jpeg
new file mode 100644
index 0000000..b5afa05
Binary files /dev/null and b/images/math/day_of_the_week.jpeg differ
diff --git a/src/math/day_of_the_week.rs b/src/math/day_of_the_week.rs
new file mode 100644
index 0000000..768d4df
--- /dev/null
+++ b/src/math/day_of_the_week.rs
@@ -0,0 +1,29 @@
+// 一周中的第几天
+// https://leetcode.cn/problems/day-of-the-week
+// INLINE  ../../images/math/day_of_the_week.jpeg
+
+pub struct Solution;
+
+impl Solution {
+    pub fn day_of_the_week(day: i32, month: i32, year: i32) -> String {
+        let week = vec![
+            "Monday",
+            "Tuesday",
+            "Wednesday",
+            "Thursday",
+            "Friday",
+            "Saturday",
+            "Sunday",
+        ];
+        let month_days = vec![31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30];
+        let mut days = 365 * (year - 1971) + (year - 1969) / 4;
+        for i in 0..(month - 1) {
+            days += month_days[i as usize];
+        }
+        if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) && month > 2 {
+            days += 1;
+        }
+        days += day;
+        return week[(days + 3) as usize % 7].to_string();
+    }
+}
diff --git a/src/math/mod.rs b/src/math/mod.rs
index 54022e9..0aff0db 100644
--- a/src/math/mod.rs
+++ b/src/math/mod.rs
@@ -18,3 +18,4 @@ pub mod find_the_pivot_integer;
 pub mod next_greater_numerically_balanced_number;
 pub mod number_of_burgers_with_no_waste_of_ingredients;
 pub mod maximum_students_taking_exam;
+pub mod day_of_the_week;
diff --git a/tests/math/day_of_the_week_test.rs b/tests/math/day_of_the_week_test.rs
new file mode 100644
index 0000000..5be2cdd
--- /dev/null
+++ b/tests/math/day_of_the_week_test.rs
@@ -0,0 +1,31 @@
+use rust_practice::math::day_of_the_week::Solution;
+
+#[test]
+fn day_of_the_week() {
+    // 示例 1：
+    // 输入：day = 31, month = 8, year = 2019
+    // 输出："Saturday"
+    let day = 31;
+    let month = 8;
+    let year = 2019;
+    let result = Solution::day_of_the_week(day, month, year);
+    assert_eq!(result, "Saturday");
+
+    // 示例 2：
+    // 输入：day = 18, month = 7, year = 1999
+    // 输出："Sunday"
+    let day = 18;
+    let month = 7;
+    let year = 1999;
+    let result = Solution::day_of_the_week(day, month, year);
+    assert_eq!(result, "Sunday");
+
+    // 示例 3：
+    // 输入：day = 15, month = 8, year = 1993
+    // 输出："Sunday"
+    let day = 15;
+    let month = 8;
+    let year = 1993;
+    let result = Solution::day_of_the_week(day, month, year);
+    assert_eq!(result, "Sunday");
+}
diff --git a/tests/math/mod.rs b/tests/math/mod.rs
index 54a37d8..99fdede 100644
--- a/tests/math/mod.rs
+++ b/tests/math/mod.rs
@@ -18,3 +18,4 @@ pub mod find_the_pivot_integer_test;
 pub mod next_greater_numerically_balanced_number_test;
 pub mod number_of_burgers_with_no_waste_of_ingredients_test;
 pub mod maximum_students_taking_exam_test;
+pub mod day_of_the_week_test;