Council of Trade Unions secretary Peter Conway said it was a busy period for some businesses, especially in the hospitality and tourism sectors.
Many people would be working and some would be trying to sort out what their holiday entitlements were.
People should, firstly, check what was in their employment agreement, as it could spell out whether they had to work and what they should be paid.
"You cannot be made to work on a public holiday, unless your agreement says so. And irrespective of what your agreement says, you must be paid at least one and a-half times what you would be normally paid for working on that day and get another paid day off at a later date," he said.
As Christmas Day and New Year's Day both fell on a Sunday, the holiday was transferred to the following Tuesday. Boxing Day and the day after New Year's Day would be observed on the days they fell.
If someone normally worked on the Sunday on which Christmas Day and New Year's Day fell this year, the public holiday was observed on the day it fell. That meant the worker was entitled to that day off on pay, Mr Conway said.
A common area of difficulty was sorting out whether a holiday was on a day that someone would usually work.
For most workers, it was obvious. But in some cases, with changing shift patterns and days of work, it was less clear.
Employers could and often did close down over the Christmas-New Year period. They could close down only once every 12 months and they could require employees to take annual leave to cover the time. The employer must have given workers at least 14 days' notice of their intention to close down, he said.
With the huge increase in insecure work - casual, temporary, fixed-term, and variable hours - and the use of texts and other informal means of communication between employers and workers, people could lose sight of their rights, Mr Conway said.
