Thanks to Karen Turner from Turner Efficiency for this awesome tip:
Do you:
Add that country’s holidays to your calendar.
Being culturally cognizant can help you successfully close a business deal, remember to wish someone well, and/or travel at low seasons for better fares.You can even add non-statutory holidays (such as International Women’s Day) or sports calendars.
Outlook 2010 & 2013
File>Options>Calendar>Add Holidays>Choose
Outlook 2003 & 2007
Tools>Options>Calendar>Add Holidays>Choose
Gmail
Google Calendar Sign in>Other Calendars>Add>Browse Interesting Calendars>Subscribe
iCal
iCal>Calendar>Find Subscriptions>Choose
OR
Calendar>Preferences>General>Show Holidays