noun
personal organiser; ring-bound planner
Refers to a loose-leaf binder system with refillable pages, such as Filofax or similar brands.
新しいシステム手帳を買って、スケジュール管理を始めた。
I bought a new personal organiser and started managing my schedule.
手帳 is a general notebook or pocket diary, while システム手帳 specifically refers to a ring-bound organiser with replaceable pages.
Compound of システム (system) and 手帳 (notebook), referring to a binder system for personal organisation.