Time-based patterns can be used to indicate the elapsed time from a start point (stopwatch), the time remaining until an end point (countdown), or simply the current time (clock).
For sighted users, a clock, countdown or stopwatch will update every second visually. For non-sighted users we must be careful not to convey this 'ticking' of the timer aurally,
You can take a look at the page notice pattern in action on our examples site.
Screen reader must not announce updates every second because this is way too verbose/noisy, and besides, it will quickly become out of sync with the onscreen content due to lag.
We must use alerts to audibly convey only the most important thresholds. For example "Less than 30 seconds left".
Alerts must be spaced at least 15 seconds apart. This will give the screen reader enough time to announce the new value, even on the slowest screen reader speech rate, in any language.
As the time pattern contains no interactive elements, there are no specific call-outs for keyboard interaction.
Without losing their current point of focus, the screen reader must be alerted of any critical points in the passage of time.
We expect to have this section content available early 2017.