diff --git a/src/lib/core.ts b/src/lib/core.ts
index 20bfca0..842f66c 100644
--- a/src/lib/core.ts
+++ b/src/lib/core.ts
@@ -86,7 +86,7 @@ export class CookieSession<SessionType = Record<string, any>> {
 		let maxAge = this.#config.cookie.maxAge;
 
 		if (this.#sessionData?.expires) {
-			maxAge = new Date(this.#sessionData.expires).getTime() / 1000 - new Date().getTime() / 1000;
+			maxAge = Math.round(new Date(this.#sessionData.expires).getTime() / 1000 - new Date().getTime() / 1000);
 		}
 
 		this.#state.needsSync = true;
@@ -143,7 +143,7 @@ export class CookieSession<SessionType = Record<string, any>> {
 		let maxAge = this.#config.cookie.maxAge;
 
 		if (this.#sessionData?.expires) {
-			maxAge = new Date(this.#sessionData.expires).getTime() / 1000 - new Date().getTime() / 1000;
+			maxAge = Math.round(new Date(this.#sessionData.expires).getTime() / 1000 - new Date().getTime() / 1000);
 		}
 
 		await this.setCookie(maxAge);
diff --git a/src/lib/utils.ts b/src/lib/utils.ts
index c7bd0a9..3dd11d9 100644
--- a/src/lib/utils.ts
+++ b/src/lib/utils.ts
@@ -5,11 +5,11 @@ import type { MaybePromise } from '@sveltejs/kit';
 export function expiresToMaxage(expires: number, expires_in: 'days' | 'hours' | 'minutes' | 'seconds') {
 	switch (expires_in) {
 		case 'days':
-			return expires * 24 * 60 * 60;
+			return Math.round(expires * 24 * 60 * 60);
 		case 'hours':
-			return expires * 60 * 60;
+			return Math.round(expires * 60 * 60);
 		case 'minutes':
-			return expires * 60;
+			return Math.round(expires * 60);
 		case 'seconds':
 			return expires;
 		default: