Wouldn't it be nice if the human society agreed to a common set of holidays but each group can give the holiday its own name and celebrate it in its own traditional way?
The following holidays would seem to be great for our current lifestyle:
1. One holiday each month.
2. Major holiday every quarter.
3. Each holiday will be on the 5th day of the week - may be the last one of the month.
4. Each major holiday will have 4th and 5th days off.
We will have the same working days - 1 to 5 with 6 and 7 being the weekend. However, some societies may call the weekend Sat/Sun, Thu/Fri or Mon/Tue or whatever their heritage demands.
No worries about which group gets how many holidays. Peace descends on Earth :)