Itsycal is a tiny menu bar calendar. If you want, it will display your events as a companion to the Mac Calendar app. Itsycal has Dark Mode, ISO week numbers, a customizable system clock replacement, and more.
Dato is a replacement for the system menu bar clock. By default, it looks exactly the same, but when you click it, you get a small calendar, calendar events, the current time in various time zones, and more.
Willed Calendar allows you to use the system's calendar and reminders in one app, as well as project management (view progress and add subtasks), event planning, chart summary and other useful features, is a great tool for your management time.
Sometimes simple calendar notifications are not enough. You need a reminder IN YOUR FACE. The app will interrupt your workflow when it is time to go to your meeting by displaying a full screen reminder showing WHAT, WHEN and WHERE.
SubClock is an improved clock menu app for mac osx. View your time in sub seconds. Minimal yet fully customizable. Change how you want to display the time.