Google calendar does a fantastic job of letting you setup reminders. However, if you are offline quite often then you Google calendar reminders might not be the best solution for you. In such a case, it is good to use a desktop based application and GMinder is an an excellent app for that purpose.
GMinder lets you manage your Google calendar even when you are offline by letting you access the desktop client. You can add events, delete events, set pop-up reminders and even browse through events to see more details.
You can also snooze or dismiss the reminders and customize their appearance by tweaking the color and sound. GMinder allows you to manage multiple Google calendars from the same desktop client. All you need to do is sign in with your Google account and your Google calendar will be downloaded for offline access.
Download GMinder here.