Add-on allows you to set your own reminders to any JIRA issue you want. Reminder is the e-mail sent to user who created reminder in the issue.
To create new reminder enter the issue and click on 'Reminder' button.
'Tonight' and 'Tomorrow' time are configured in Reminders Settings menu under your avatar (Morning time for tomorrow and Evening time for tonight):
If you have the "Create reminders for groups" permission, you can select the group name in the Who field
If you want to make reminders regular,
Menu under your avatar shows you all reminders created by you.