広場投稿追加画面の刷新 (#399) (#413)

Reviewed-on: #413
Co-authored-by: miteruzo <miteruzo@naver.com>
Co-committed-by: miteruzo <miteruzo@naver.com>

frontend/src/components/common/DateTimeField.test.tsx

@@ -21,7 +21,8 @@ describe ('DateTimeField', () => {
     fireEvent.change (input, { target: { value: '' } })
 
     const first = handleChange.mock.calls[0]?.[0]
-    expect (new Date (first).getFullYear ()).toBe (2026)
+    expect (first).toMatch (/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}Z$/)
+    expect (new Date (first).getUTCSeconds ()).toBe (0)
     expect (handleChange).toHaveBeenLastCalledWith (null)
   })
 })