I used to put work ones on but I can't now remember how. And on consideration I find it better for building friendly personal relationships with project managers who send me work to e-mail them individually with my holiday dates. Many of my clients have some sort of online system where I can add holidays to a calendar so they don't contact me for a particular period. Scandinavians also expect me to take a long summer break and will have been asking me to tell them when I am taking it since about May. There will be a lot of "did you have a peaceful holiday" e-mails going around from when everyone comes back in mid-August and those sort of brief personal exchanges are also good for building relationships now that a lot of business contact is via anonymous platforms.