ReminderFox is an easy to use and simple add-on for Mozilla Firefox for scheduling tasks and reminders.
Download and install it from here.
After installing, it will show up in the bottom right corner of Firefox.
To schedule events and reminders, click on it and select “Add event”. Select appropriate date and time as well as frequency of event and whether alarm is needed or not and hit “Save”. Alternatively, right click on ReminderFox and then add reminders as well as customize further options.
The saved event will now display when the mouse is hovered over Reminder Fox displaying the event schedule.
There are other useful features like importing and exporting calendar files (files with .ics format) and sharing them over a network. Most of this functionality is limited but is incorporated should it be required. The settings for these can be accessed through right clicking on ReminderFox > Options.
Overall, a very useful and light add-on that can help in organizing and keeping track of reminders for various tasks directly through Firefox.