Legal Question in Employment Law in New York

Neither. It would depend on where you work (government, private practice, union, non-union etc. etc.) and the rules they have established etc. For example, the NYSE rules provide that if a holiday is on the weekend the holiday it would normally be observed on the Friday before (and the stock market would thus be closed) unless the Friday is the last trading day of the quarter or of the year, in which case the market is open on both the Friday and the Monday. As such, for 2010, people working on wall street likely had to work on both Friday and Monday.