Set Update Limits on iCalendar Feed

Question

I have a calendar feed (.ics) available from my application, but it\'s quite large since it includes over 4,000 events. Is there a standard or best practice when it comes t

Answer 1

To only check for updates hourly (for example) use this in your VCALENDAR file:

X-PUBLISHED-TTL:PT1H

I gleaned this information from one of the Microsoft Protocol documents [MS-OXCICAL]: iCalendar to Appointment Object Conversion Protocol Specification (download the linked PDF)

2.1.3.1.1.15 Property: X-PUBLISHED-TTL

RFC Reference: N/A

Number of Instances Allowed: 0, 1

Format: Duration ([RFC2445] section 4.3.6)

Brief Description: Specifies a suggested iCalendar file download frequency for clients and servers with sync capabilities.

Importing to Calendar objects
This property SHOULD<32> be ignored.

Exporting from Calendar objects
If this iCalendar is being automatically published to a remote location at regular intervals, this property SHOULD<33> be set to that interval with a minimum granularity of minutes.

Answer 2

RFC 7986 introduced a new REFRESH-INTERVAL property:

https://tools.ietf.org/html/rfc7986#section-5.7

I don't know if this is supported by any clients, but the RFC was authored by Apple, so I assume they have some interest in this.