Here's an answer to a slightly different question: **"The starting date for my new job in the Netherlands is on the 1st of the month, which is a Saturday. Does that mean I have to come to work on a Saturday?"** It's not the question you asked, but the cultural context is relevant enough that I think you should get this answer, too.

Your contract probably starts on the 1st of the month because Dutch agreements for office work are normally measured in calendar months: you sign a contract for x months, and you get paid near the end of every calendar month. Because of this, it is common to choose 'the 1st of [month]' as a starting date for a contract, even when that is a weekend day or a day you would not normally work (if you work less than 5 days a week). It's just a really nice date to work with, and avoids the need for handling a first month that is partial. Makes it easy to remember when your contract is about to end, too.

So, that's how you get contracts that start on Saturday-the-1sts. (Or on a Monday-the-1st when you work 32h Tue-Fri -- similar situation.) Whether your first working day will also be that Saturday depends on what sort of job it is, and what sort of employer. Send them an e-mail and ask; for how to write such an e-mail, see the answers that *do* deal with 'how to ask if it is a holiday'. :-)