fix(_createdAt/_updatedAt): fields are now ISO format

ts/00_commitinfo_data.ts

@@ -3,6 +3,6 @@
  */
 export const commitinfo = {
   name: '@push.rocks/smartdata',
-  version: '5.1.1',
+  version: '5.1.2',
   description: 'An advanced library for NoSQL data organization and manipulation using TypeScript with support for MongoDB, data validation, collections, and custom data types.'
 }

ts/smartdata.classes.doc.ts

@@ -192,13 +192,13 @@ export class SmartDataDbDoc<T extends TImplements, TImplements, TManager extends
    * updated from db in any case where doc comes from db
    */
   @svDb()
-  _createdAt: number = Date.now();
+  _createdAt: string = (new Date()).toISOString();
 
   /**
    * will be updated everytime the doc is saved
    */
   @svDb()
-  _updatedAt: number = Date.now();
+  _updatedAt: string = (new Date()).toISOString();
 
   /**
    * unique indexes
@@ -234,7 +234,7 @@ export class SmartDataDbDoc<T extends TImplements, TImplements, TManager extends
     const self: any = this;
     let dbResult: any;
 
-    this._updatedAt = Date.now();
+    this._updatedAt = (new Date()).toISOString();
 
     switch (this.creationStatus) {
       case 'db':