I write a list of duties, either in my diary or on a piece of paper kept face-up on my diary. By duties, I do not mean habituated household tasks, those do not need reminders, but irregular, important events which I might forget. Although urgent tasks would be included, most of the list comprises jobs which are not urgent but need attention sooner or later, and it might as well be sooner. I use the same technique, but on a different piece of paper, for a shopping list, to which I add items as soon as I think of them and cross them off when they are bought.
As I invariably use my diary every day I am reminded of duties until I carry them out and cross them off the list. Computers, alarms and the like are unnecessary for me. My son practically lives on his phone, computer, iPad and so on, and uses all manner of time management software for anything from budgets to exercise, to absolutely no avail. His energy goes into using the software instead of doing the tasks. Simple methods are best.