If you view some of your published calendars in a web browser and leave it without any intervention, clicking on dates displayed within published calendar, you will not see newer published items. Unless you indeed manually refresh the browser or click on any date and back to desired one where new item was created in the GW mailbox by the owner.
Locate the calhost.cfg file (/var/opt/novell/groupwise/calhost) and edit it by a text editor. Search for "refresh" and you will find that by default the content is not set to refresh automatically.
You can set it some some value in seconds, save the file and restart grpwise-tomcat part to take effect of this change.
The browser will be then auto-refreshing its content periodically as specified.