[No show up for work no get money ,LOL]
Periodically send out a mass email. Anyone not on authorized leave that does not respond in 30 minutes is terminated.
Would have to be 3.5 hours, due to U.S. time zones. Then there's Hawaii...
When I worked for a global company, there were many times when I didn't get to sleep through the night because one person in a workgroup was calling from London and another was working in Japan, and I was midway between—and, as a contractor, was the "low person" on the totem pole.