One Calendar

It's a fine calendar, but there are some usability hurdles. When launching the app by clicking on the widget, it will often launch the app in the last place you left off rather than the event you select on the widget. Also there's no assistance when entering addresses onto events. And to open a map with an event's location, you need to be in edit mode on the event.

Works well and easy to use. I have been using this for over 5 years and this has been a lifesaver for scheduling appointments. So far it has been better than using a paper calendar. When I have to change a date or time it is easy to go in and make the edits without having to erase or even use whiteout. I like that it gives you the option to have the calendar remind you in advance when your appointment starts or when your event is starting.

Works well to sync Google calendar, Outlook and Windows 10 calendar apps. I haven't tried it with others. Syncs best if you enter the appointment in One calendar first. It doesn't always pick up entries that you put into other calendars. If you have multiple calendar apps on your phone, tablet or computer, it will result in multiple reminders. I don't know how to get around that. For reminders from OneCalendar you have to go into the calendar entry to change the reminder time. I have not found a simple way to delay the reminder when it appears. If you are out of cell coverage, calendar is slow to load because it cannot sync.