I would refer to my Employee Manual. If there are no special policies allowing those with the most years of service in the department to choose favored PTO dates before anyone else, then that's your answer. Having the most days based on years of service is not the same as having priority in choosing days off. That's normally at the discretion of the manager and based on who asks first. If the policy doesn't explicitly state that, then I would ask HR for a clarification and give them a deadline to provide it to you. My guess is that's the answer you'll get. Next, go to your manager and review the problem, your plan, and the policy with them to get their buy-in so that if and when one of those managers goes over your head, the answer is the same. After that, it's time to lead and create some boundaries. Sit all three of them down in the same meeting. (Do this now so that the policy is clear to them for the rest of the year and they have time to consider how they will use their PTO.) Let them know that there is no easy way to describe how much you value each of them and how grateful you are for their years of service to the company. It's extraordinary and it's to be commended, but that you are unwilling to spend another calendar year with resentment over the vacation policy. It degrades the team atmosphere that you value and it's unacceptable from department leaders who model behavior for other employees. Let them know that you've met with HR and your boss prior to reviewing the policy with them. The policy you are about to review is *THE* policy. There will be no further discussion about how it will be administered unless the company changes it. Read the policy aloud, including HR's clarification and give them copies. Document that they received those copies. State plainly that the department vacation policy, especially as it relates to the holidays, will no longer be based on seniority. Instead, it will be approved on a first come, first served basis, date stamped and signed, copies kept, and will be subject to change should the business not have adequate coverage. If you want to go the extra mile, throw them a bone. Be willing to offer each manager who doesn't get their Christmas days one day during a few weeks of that time where you fill in for them so that they can take a vacation day. Let them know what dates will not be available and that they cannot select the same day. In return, tell them that your expectation for the year is that they work on working better together to resolve differences and present a united front to the rest of the team. Don't be held hostage by those who report to you, no matter how long they've been with the company. And be clear in what you want. They may not like you for it, but being liked should never be a goal of someone in leadership. If it happens, that's great, but the goal is offer others respect and to be respected in return.