Calendars aimed at desktops are somewhat rare and so most people who need reminders use either cloud-based or cloud-based solutions. schedule warning emails to themselves or work with the calendar app on their mobile phone.
If instead of the above solutions you prefer an application on your computer that works without internet connection, without synchronizing your contact list and other personal data, you may want to take a look at RemindMe.
The RemindMe is a calendar application for desktop computers, open source, for Windows. The program is minimized when it starts and you can access it by double-clicking its icon in the taskbar. It has a sidebar and a tab bar at the bottom.
With RemidMe you can set reminders by entering a title and selecting the date and time of the reminder. Reminders can be set to repeat every day, only daily, per month or on specific dates. Of course you can add a note to the reminder.
You can view all your created reminders at any time, preview a reminder, make a copy, delete a reminder, postpone it, go to the next date, turn it on or off. It even has a countdown timer to receive a reminder in no time.
The application has a built-in feature that allows you to run a batch file Windows (.Bat) when the reminder is activated. This is an interesting way to automate various tasks.
The pop-up notification size can be customized. RemidMe lets you customize width, height, title font, pop-up description font. You can even see the changes you have made in the notifications window as a preview before saving them.