Sunday, January 22, 2012

[Gd] Calendar API v3 Best Practices: Reminders

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Google Apps Developer Blog: Calendar API v3 Best Practices: Reminders

We recently posted some best practices for working with recurring events in Google Calendar API v3. In this blog post we’ll highlight another improved area in the v3 API: event reminders.


Google Calendar API v3 offers developers flexible control over event reminders, including per-calendar default settings and custom overrides for individual events.

The user’s default reminders for events on a given calendar can be found in the corresponding entry in the Calendar List collection. The Calendar List collection acts a bit like a list of bookmarks, containing entries for the calendars that the user owns or has looked at in the past (it corresponds to the content of the "My Calendars" and "Other Calendars" list on the bottom left in the Web version of Google Calendar). Each entry is annotated with user-specific settings for the individual calendar, such as the preferred color in the UI and the default reminders.

Google Calendar currently supports three ways of reminding its users of events: "popup", prompting a message directly in the browser, mobile phone or desktop client, as well as "email" and "sms" for messages sent through the respective channels. To change the defaults, update the Calendar List entry and include the reminder method and how many minutes in advance the user should be alerted. In the following example, we set an email reminder to be sent 60 minutes before an event, and a popup reminder 10 minutes before.

"summary": "Work Calendar",
"defaultReminders": [
"method": "email",
"minutes": 60
"method": "popup",
"minutes": 10
A Calendar List entry with title and default reminders.

The default reminders will be applied to all existing and future events on this calendar, provided they don’t have custom reminders set already. In contrast to earlier versions of the API, newly created events will also have reminders set by default.

Sometimes, there are events that we want a special reminder for, or none at all. To override the defaults for a specific event, switch the useDefault flag in the reminders section to false, and include a set of custom reminders, or leave the list empty. When you define a set of override reminders for a recurring series, they are automatically applied to each of its occurrences, unless they have been overridden explicitly. Like the default reminders on the calendar, these are personal reminders for the user that is logged in, and will not influence the settings others might have for the same calendar or event. Here is an example that overrides the default reminders with a 15 minute SMS reminder for that specific event.

"summary": "API Office Hours",
"reminders": {
"useDefault": false,
"overrides": [
"method": "sms",
"minutes": 15
An event representation with title and reminder overrides.

The defaults for the given calendar are included at the top of any event listing result. This way, reminder settings for all events in the result can be determined by the client without having to make the additional API call to the corresponding entry in the Calendar List collection.

In this post and an earlier post about best practices with recurring events, we have covered some improved areas of the latest version of the Google Calendar API. Have a look at the migration guide for a more complete view of other changes we made in the new version, and let us know what you think.

If you have any questions about handling reminders or other features of the new Calendar API, post them on the Calendar API forum.

Peter Lundblad   profile

Peter joined Google in 2006. He's been leading the Calendar API team for the last 2 years. He's previously worked on video uploads for YouTube.

Fabian Schlup   profile

Fabian is a Software Engineer at Google in Z├╝rich, working on Calendar and Tasks, with a focus on APIs.


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