Monday Work Etiquette #2, On Time Zones, Customs and Holidays

We tend to live in our cocoon and forget that it might be Winter someplace while we are still enjoying Summer here in the US.
 
Today's holiday here, Labor Day is celebrated in most countries on May 1st.
Some are sleeping or might already be starting their Tuesday run.
Holidays and customs that are unknown to us might be very important to others.