diff --git a/src/CronDate.ts b/src/CronDate.ts
index 2d5af91..dfadb99 100644
--- a/src/CronDate.ts
+++ b/src/CronDate.ts
@@ -169,7 +169,7 @@ export class CronDate {
    * Adds one second to the current CronDate.
    */
   addSecond(): void {
-    this.#date = this.#date.plus({ seconds: 1 });
+    this.#date = this.#date.plus({ seconds: 1 }).startOf('second');
   }
 
   /**
@@ -216,7 +216,7 @@ export class CronDate {
    * If the second is 0, it will subtract one minute instead.
    */
   subtractSecond(): void {
-    this.#date = this.#date.minus({ seconds: 1 });
+    this.#date = this.#date.minus({ seconds: 1 }).startOf('second');
   }
 
   /**