Most employment is "at will". This means that an employer can set the conditions of work much as it sees fit; this inlcudes the use of sick time or other PTO. The fact is that such time is typiclly not mandated to be given under the law. Therefore, to the extent that a company chooses to provide it, it has a great deal of say in over when and wyy it is taken. Accordingly, unless your employer's action violated a union agreement or employment contract or constitutes some form of legally actionable discrimination, it was legal.