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The RSS 2.0 spec says the channel element can optionally have skipDays and/or skipHours elements. Here’s what it says for skipDays:

skipDays
An XML element that contains up to seven sub-elements whose value is Monday, Tuesday, Wednesday, Thursday, Friday, Saturday or Sunday. Aggregators may not read the channel during days listed in the skipDays element.

As I understand it, the motivation behind these elements it to let aggregators know that they needn’t bother updating the channel at the given times or on the given days, because the author will be asleep (or otherwise occupied) and the content won’t change.

However, this assumes that the aggregator is updating at other times. What if, for example, a feed exists for a weekly newsletter published every Tuesday. The feed author could add a skipDays element to the channel to tell aggregators not to bother updating on any day but Tuesday, thus saving a lot of bandwidth through the rest of the week. But that won’t work. Anyone who doesn’t fire up their aggregator on a Tuesday (e.g. somebody who doesn’t work Tuesdays) won’t get the newsletter.

Similarly, if you were to use the skipHours element to say to aggregators “don’t update outside of my office hours”, you’ll be cutting out everyone who doesn’t use their aggregator during your office hours. Extrapolating further, for every hour or day you put in skipHours/skipDays you’ll be losing all the subscribers who happen to use their aggregators only at those times/on those days.

Perhaps this hasn’t been an issue due to the types of people who are using RSS at the moment, but this will change as RSS hits the big time and reaches consumers desktops. For example, my parents tend to use their computer for around 30 minutes in the evening, so once they start using RSS they could easily miss out on entire feeds skipping just one hour.

So, I think that skipHours and skipDays are useless in their current form. Far more useful would be a redefinition from “don’t read this channel at these times” to “the channel will not be updated at these times.” Aggregators can then use that information to save bandwidth whilst not missing anything, no matter when they’re run.

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