I work at a fairly large company (1000+ employees all on a single campus of multiple buildings). I am interviewing for a new position in the same company, and need to take a vacation day. My boss is asking why I need the day, and I don't really want to tell him that it is for the interview. It is unlikely that I will be seen at the company grounds by my boss during the interview day, but it is still possible. What do I do?
I've thought about making up an excuse for why I need to be home, but that feels wrong and it will really be bad if I run into anyone during the interview day...
**EDIT: Taking time off at my job is semi-complicated. We are working on a project at the moment and while it is not impossible to take time off, we are discouraged from doing so until the project is over. Usually, my job happens in cycles, so like 3 months on a project, 1 month to gear up for the next one, then maybe 6 months/2 months and so on. So we definitely can take our vacation days, but doing so during a project is frowned upon.