What's the Time?
Collaboration is very much about being able to meet at a single time from anywhere in the world. It's also about counting down to a kick off. These tools will assist. They are all similar so the one you choose will really be a matter of preference.
World Time Server
Shows current time and date in cities and countries in all time zones, automatically adjusted for local Daylight Saving Time rules. Convert times from one location to another or even check current international weather conditions. I've used this one personally for many years.
TimeandDate.com
Contains time zone and date converters, world clock, calendar etc. One very handy tool is the Event Time Announcer to show local times worldwide for your event. Mobile device apps available.