diff --git a/CHANGELOG.md b/CHANGELOG.md
index ee249c877..79a29a98f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 - Accounting data is now built each night and saved in database
 - OpenAPI endpoint to fetch accounting data
 - Fix a bug: providing an array of attributes to filter OpenApi data, results in error
+- Fix a bug: unable to manage stocks on new products
 - [TODO DEPLOY] `rails fablab:setup:build_accounting_lines`
 
 - Add reservation deadline parameter (#414)
diff --git a/app/frontend/src/javascript/lib/format.ts b/app/frontend/src/javascript/lib/format.ts
index ddf199aeb..adb6ee777 100644
--- a/app/frontend/src/javascript/lib/format.ts
+++ b/app/frontend/src/javascript/lib/format.ts
@@ -5,6 +5,29 @@ import { TDateISO, TDateISODate, THours, TMinutes } from '../typings/date-iso';
 declare let Fablab: IFablab;
 
 export default class FormatLib {
+  /**
+   * Check if the provided variable is a JS Date oject
+   */
+  static isDate = (value: unknown): boolean => {
+    return (value != null) && !isNaN(value as number) && (typeof (value as Date).getDate !== 'undefined');
+  };
+
+  /**
+   * Check if the provided variable is an ISO 8601 representation of a date
+   */
+  static isDateISO = (value: string): boolean => {
+    if (typeof value !== 'string') return false;
+    return !!value?.match(/^\d\d\d\d-\d\d-\d\dT\d\d:\d\d:\d\d.\d\d\d/);
+  };
+
+  /**
+   * Check if the provided variable is string representing a short time, according to ISO 8601 (e.g. 14:21)
+   */
+  static isShortTimeISO = (value: string): boolean => {
+    if (typeof value !== 'string') return false;
+    return !!value?.match(/^\d\d:\d\d$/);
+  };
+
   /**
    * Return the formatted localized date for the given date
    */
@@ -17,8 +40,8 @@ export default class FormatLib {
    */
   static time = (date: Date|TDateISO|`${THours}:${TMinutes}`): string => {
     let tempDate: Date;
-    const isoTimeMatch = (date as string)?.match(/^(\d\d):(\d\d)$/);
-    if (isoTimeMatch) {
+    if (FormatLib.isShortTimeISO(date as string)) {
+      const isoTimeMatch = (date as string)?.match(/^(\d\d):(\d\d)$/);
       tempDate = new Date();
       tempDate.setHours(parseInt(isoTimeMatch[1], 10));
       tempDate.setMinutes(parseInt(isoTimeMatch[2], 10));