diff --git a/src/modules/record/interfaces/recordable.ts b/src/modules/record/interfaces/recordable.ts
index 66a9c8a..696b410 100644
--- a/src/modules/record/interfaces/recordable.ts
+++ b/src/modules/record/interfaces/recordable.ts
@@ -1,7 +1,9 @@
+import type { ISODate } from '@/shared/types/date'
+
 export interface Recordable {
   id: string
   taskId: string
-  start: Date
-  end?: Date
-  stepRecords: Record<string, { start: Date; end?: Date }>
+  start: ISODate
+  end?: ISODate
+  stepRecords: Record<string, { start: ISODate; end?: ISODate }>
 }
diff --git a/src/modules/record/models/task-record.ts b/src/modules/record/models/task-record.ts
index 399e0f7..2c89953 100644
--- a/src/modules/record/models/task-record.ts
+++ b/src/modules/record/models/task-record.ts
@@ -1,9 +1,10 @@
+import { toISODate, type ISODate } from '@/shared/types/date'
 import type { Recordable } from '../interfaces/recordable'
 
 export class TaskRecord implements Recordable {
-  public start: Date = new Date()
-  public end: Date | undefined = undefined
-  public stepRecords: Record<string, { start: Date; end?: Date }> = {}
+  public start: ISODate = toISODate(new Date())
+  public end: ISODate | undefined = undefined
+  public stepRecords: Record<string, { start: ISODate; end?: ISODate }> = {}
 
   public constructor(
     public readonly id: string,
@@ -15,7 +16,8 @@ export class TaskRecord implements Recordable {
       return null
     }
 
-    const durationMilliseconds = this.end.getTime() - this.start.getTime()
+    const durationMilliseconds =
+      new Date(this.end).getTime() - new Date(this.start).getTime()
 
     return Math.round(durationMilliseconds / (1000 * 60))
   }
diff --git a/src/modules/record/stores/useTaskRecordStore.ts b/src/modules/record/stores/useTaskRecordStore.ts
index 63a7e2a..d9e1339 100644
--- a/src/modules/record/stores/useTaskRecordStore.ts
+++ b/src/modules/record/stores/useTaskRecordStore.ts
@@ -1,15 +1,8 @@
 import { defineStore } from 'pinia'
 import type { Recordable } from '../interfaces/recordable'
 
-interface StoredTaskRecordable
-  extends Omit<Recordable, 'start' | 'end' | 'stepRecords'> {
-  start: string
-  end?: string
-  stepRecords: Record<string, { start: string; end?: string }>
-}
-
 export interface TaskRecordStoreState {
-  records: { [taskId: string]: StoredTaskRecordable[] }
+  records: { [taskId: string]: Recordable[] }
 }
 
 export const useTaskRecordStore = defineStore('task-record-store', {
diff --git a/src/shared/types/date.ts b/src/shared/types/date.ts
new file mode 100644
index 0000000..ef0f185
--- /dev/null
+++ b/src/shared/types/date.ts
@@ -0,0 +1,3 @@
+export type ISODate = string
+
+export const toISODate = (date: Date): ISODate => date.toISOString()