Time is an important design variable to understand. Your user experience is effected by it no matter what user experience you are serving up and the rules are different for every context. For example, the "three click rule" (users must get to their destination within three clicks) applies to e-commerce primarily but not to mortgage education, financial services usability or reading the New York Times online.
Time Usability 101: Design for asynchronous interaction. Asynchronous means users don't do it all in one setting. Environmental distraction is inherent to any user experience: the pasta is burning, the kids are screaming, the documents are being tracked down, printer cartridge is being changed, someone interrupts...
Here is some fascinating research about conversion rates and the influence of time:
Up to 85 percent of conversions occur after the day the most recent advertising impression was served, according to new research from Advertising.com. The results seem to show online ads can have an impact on buyers' purchasing decisions long after they view an ad.
For the five-day monitoring period, approximately one-third of all conversions happened on the same day that the impression was served, but only nine to 11 percent occurred within three hours of the impression being served. The longer periods of monitoring revealed that up to 85 percent of conversions occurred days after a user was served an impression.
"These findings show what a significant portion of conversion activity takes place well beyond the impression," said Scott Ferber, chief executive officer of Advertising.com. He said that the data shows that metrics such as per-click or per-action may not give marketers an accurate picture of campaign results. "It also reveals how lasting the effect of an impression can be," he said.
This data supports the theory that users' consumption of the Internet is often patterned and repeated on a daily basis.
If you know when your audience is going to be online or converting, there is some value to targeting by time of day."
The implications for web analytics analysis, advertising and content management are interesting:
1) Ad impressions go through a 48 hour or so window of decision making activity. Decision making being influenced by time and potentially access to external information, persons or environments.
2) Interpreting user behavior through a web analytics perspective ought to include a sensitivity for the impact of time (i.e. conversion rates are non-local meaning they aren't isolated to immediate on-page actions as is the current view of traffic log analysis).
3) Understand how you are supporting time usability. Do you offer good time-out messages, good error protection from browser instability (if serving a web based application)? Does your content support good decision making across time?
4) Consider your website usability strategy as a variety of ad impression. Already, independent studies show that website usability (ease of use) increases the likelihood of purchase. More on this later.
5) Get ahead of the competition and synchronize ad impressions with conversion behavior. In other words, throw out the purchase cycle across time and serve up product and service content that parallels return visitor activity. In some cases with high ticket software solutions, getting clear about this may lead to strategic leaps in revenue generation that otherwise was pegged as just low conversion.
If you'd like to check out the science of time usability, have a skim of this paper (PDF 196K) Daniel Loewus-Deitch and I (Frank Spillers) published at the workshop on the Temporal Aspects of Tasks in September at HCI 2003 in Bath, England.