I think you have different options and it can depend on their working pattern and how you allocate leave for part time folk at the moment.

If they are .6 and normally work monday, tuesday and wednesday, then the thursday and friday are their non working days anyway. So if you credit them with .6 of 3 days worth of hours, they will have some left over. But if someone normally works wednesday, thursday and friday, they will owe some.

The fairest way is to calculate it in hours and they then deduct the number of hours they actually have to book off. If you already do leave this way for part time folk this is the easiest, as people will be used to that process.

The alternative is just to say that you are closed that period and whatever your working pattern, you just don't have to come in. As with many things in our world, you will have some people happy and some people unhappy.

I would tend to recommend Teresa's second option in cases like this.

Effectively, those days aren't "holidays" in the contractual sense. They are a discretionary closedown. The office isn't open. People don't get to choose to come to work if they want to. It's more like additional weekend days (of which, of course, everyone takes two per week regardless of their contractual hours).

There are some legal technicalities that could be argued over this solution but the odds of one of these part-timers complaining about free days off are so small that you can safely ignore them.

Thank you Teresa and Robey for your advice.

Much appreciated.

In reply to Caitlin:

I have a similar situation to this, but it appears to me that if the days between christmas and new year are non working days anyway these employees are going to be a bit pissed off i.e others that work the same number of days a week but on different days are benefiting from extra paid time off as are the full timers - how should I tackle this?

In reply to Robey:

We had this situation during Covid - we wanted to recognise the incredibly tough year people had had, and 'give' them the three days leave over Christmas as a 'wellbeing break'. We had a slight complication in that we also have front line staff who would be needed to provide services those three days, so we agreed that anyone who was required to work could take the three days in Jan / Feb (but they should be three consecutive days so they got the same break).
We had a lot of debate over impact on part time people and whether to pro-rata the three days. The senior management really wanted just for everyone to have the 3-day break but in HR we did consider the possible implications.
On working through some examples, we realised that if the three days were pro-rated, there was the possibility that depending on their work pattern, some people would have had to use some of their leave entitlement to cover the full three days; whereas others who worked the same number of hours per week but over a different pattern, would not have had to use leave. That didn't seem fair; but by not pro-rating the three days, ultimately everyone benefitted from getting some extra time off.
The only way someone wouldn't benefit from the approach was if they worked 2 days a week, on Monday and Friday (because those were the Bank Hol days that year). I honestly didn't think that would apply to anyone, but incredibly there did turn out to be one person with that work pattern! As a way forward we agreed she could have two days to take in Jan / Feb.
We were very careful not to refer to the additional three days as 'additional leave' i.e. added to your annual entitlement, but that it was very much a 'wellbeing break' which I think did help people understand the rationale for not applying a pro-rata for part-time staff. In the end it went down really well, to the extent that we had some grumbling when we didn't do it again the next year - although it wasn't raised again after that. So if you're definitely only doing it as a one-off I would suggest being very clear on that, but still be prepared for it to be raised next year.