Editor's note: Amy Gahran writes about mobile tech for CNN.com. She is a San Francisco Bay Area writer and media consultant whose blog, Contentious.com, explores how people communicate in the online age.
(CNN) -- When online media first arose, one of the common complaints about it was that it wasn't very portable. Unlike books or magazines, you couldn't easily read your desktop or laptop on the bus or in the bathroom.
But mobile digital media hold the promise of a return to convenient portable reading. And new statistics from the popular online reading list service ReadItLater indicate that mobile devices are not only changing where people are reading but when.
ReadItLater is a free service that allows internet users to save the full text of articles and other content they encounter online on a personal reading list. It then displays this content in a format that's very friendly to mobile devices.
I use ReadItLater (and one of its competitors, Instapaper) to save longer-format content (like 5,000-word Harper's articles) for later digital reading in a way that I find easier on the eyes than extended reading sessions on a Web browser.
Almost always, this means reading articles on my Android phone -- usually when I'm on public transit or waiting in line somewhere but often also when I'm lying in bed.
According to a recent ReadItLater blog post, users of this service save articles to their lists at a fairly constant pace throughout the day, but they read this content mostly in the evening, from 6 to 9 p.m.
But when ReadItLater took a close look at statistics for its iPhone and iPad users, a different trend emerged.
For iPhone users, there tended to be four peak reading times:
• 6 a.m.: Early morning, breakfast
• 9 a.m.: Morning commute, start of the workday
• 5-6 p.m.: End of the workday, commute home
• 8-10 p.m.: Couch time, prime time, bedtime
"In reality, this really is a graph of whitespace time," says the post. "Whitespace is the time between A and B. It's the time on the subway or bus. It's the time standing in line. It's a spare moment."
For iPad users, ReadItLater noticed one especially huge peak reading time: 8 to 10 p.m. "This time slot is the same one coveted by television. When the majority of people are consuming content it seems perfectly natural that people would use this time to do their reading as well."
ReadItLater also found that "iPad owners are no longer doing the majority of their reading on their computers."
This makes sense to me, since iPads are primarily media consumption devices while computers and smartphones are better suited for communication and content creation.
ReadItLater did not offer statistics for Android devices, but this service does not offer its own Android app. The NewsRoom Android app by Trileet Inc. is supported by the ReadItLater API and is one option for Android users.
The opinions expressed in this post are solely those of Amy Gahran. Thanks to Sonya Quick of the Orange County Register for bringing the ReadItLater post to my attention.