diff --git a/server-rs/crates/module-runtime/src/civil_calendar.rs b/server-rs/crates/module-runtime/src/civil_calendar.rs
index 5b43da801..e4a679e5a 100644
--- a/server-rs/crates/module-runtime/src/civil_calendar.rs
+++ b/server-rs/crates/module-runtime/src/civil_calendar.rs
@@ -20,17 +20,20 @@ pub fn is_leap_year(year: i32) -> bool {
 }
 
 /// 公历年月日 → 1970-01-01 起的日序号。
+///
+/// 全程用 `i64` 运算：`i32` 年份区间内 `era * 146_097` 会超过 `i32::MAX`，在 `i32` 下
+/// 会溢出（debug panic、release 静默回绕），因此这里的中间量一律提升到 `i64`。
 pub fn days_from_civil(year: i32, month: u8, day: u8) -> i64 {
     // 中文注释：Howard Hinnant civil calendar 算法，返回 1970-01-01 起的日序号。
-    let adjusted_year = year - if month <= 2 { 1 } else { 0 };
+    let adjusted_year = i64::from(year) - if month <= 2 { 1 } else { 0 };
     let era = adjusted_year.div_euclid(400);
     let year_of_era = adjusted_year - era * 400;
-    let month = i32::from(month);
-    let day = i32::from(day);
+    let month = i64::from(month);
+    let day = i64::from(day);
     let month_prime = month + if month > 2 { -3 } else { 9 };
     let day_of_year = (153 * month_prime + 2) / 5 + day - 1;
     let day_of_era = year_of_era * 365 + year_of_era / 4 - year_of_era / 100 + day_of_year;
-    i64::from(era * 146_097 + day_of_era - 719_468)
+    era * 146_097 + day_of_era - 719_468
 }
 
 /// 1970-01-01 起的日序号 → 公历年月日。
@@ -79,6 +82,21 @@ mod tests {
         }
     }
 
+    #[test]
+    fn days_from_civil_handles_full_i32_year_range_without_overflow() {
+        // 中文注释：i32 年份区间内的 era 乘法会超过 i32::MAX，必须提升到 i64 才不溢出。
+        for (year, month, day) in [
+            (i32::MIN, 1, 1),
+            (i32::MIN, 2, 29),
+            (i32::MIN, 12, 31),
+            (i32::MAX, 1, 1),
+            (i32::MAX, 12, 31),
+        ] {
+            let date_key = days_from_civil(year, month, day);
+            assert_eq!(civil_from_days(date_key), (year, month, day));
+        }
+    }
+
     #[test]
     fn days_in_month_applies_leap_year_rules() {
         assert_eq!(days_in_month(2024, 2), 29);