I'm surprised I haven't seen this mentioned so it may be something specific to my site...but:
We're using the clock block (6.x-1.x-dev) on a page which anonymous users view and automatically is refreshed every 15 minutes or so (using a browser plugin).
The problem appears to be that the clock block is cached and, when the browser refreshes, the clock displays an incorrect time: it displays the time the page was cached as it's starting time (and then starts running up via .js from that point) rather than the actual time. As soon as the caches are cleared or cron runs, a refresh shows the proper time.
As an example:
- Cron runs at 2pm
- Page with clock loads at 2pm
- .js starts counting up, so it shows the correct time
- At 2:15pm the page properly shows 2:15 as the time because the .js counted up, HOWEVER, then at 2:15 the page refreshes and...
- ....at this point, the clock displays 2pm again, and starts counting up again
So, I'm not sure if the answer is to simply disable caching on the block? Or does this have more to do with full page caching?
Not sure how to address this, I'd help write a patch if I knew where to look. Any ideas?