About every seven years, depending on leap years, Christmas is celebrated on a Monday. Unlike the sacred triduum, which moves about the calendar and can land anytime from early spring to late April, the date of Christmas is quite set: Dec. 25. Because of this, parishes and pastors find themselves this year in the unenviable position of celebrating the Solemnity of Christmas only hours after lighting the final candle on the Advent wreath.

I say unenviable because celebrating the sacred liturgy well requires effort and preparation. The Fourth Sunday of Advent is an important liturgical day, and it deserves its own repertoire, decoration and tone, not to mention its own homily. Without a doubt, Christmas deserves just as much effort; indeed, due to its special character and significance, it requires even more. So try not to be too hard on your pastor, choir director and church decorators if they seem a little worn out on Christmas Tuesday.

It’s a truth worthy of reflection — celebrating well requires labor. I do not mean ordinary revelry, which requires little planning or the prudent expenditure of energy. I mean the kind of celebrations we expect at wedding feasts and family holiday reunions. Most great celebrations do not simply come together at the last minute on their own, nor do they result in lifelong memories without the sacrifices of many. To party hearty often requires hearty work. For the Christian, part of the work of truly celebrating is offering God our worship for the gift of family, faith and salvation.

The sacred liturgy is not a spectator sport; it is work, the most sublime of work, for by means of it we participate in the salvation of the world. It requires the gift of self, which is no easy task.

Because the sacred liturgy is work, we naturally at times look for ways to avoid it, or to make it accommodate our own desires and harried schedules. And so it is not uncommon to be asked, when Christmas falls on a Monday, whether the Christian could satisfy his or her obligation to attend Mass for both the Fourth Sunday of Advent and Christmas by attending one Mass on Sunday night.

The logic behind the question is reasonable: The Church clearly allows for Saturday vigil Masses to satisfy the Sunday obligation. So why wouldn’t she also allow for the Mass on Sunday evening to satisfy the obligation on Monday, even when one is attending Mass to satisfy the Sunday obligation? (Get all that?)

Certainly it would be for the best if we remembered that the Mass is that place of privileged encounter and communion between God and the people he has chosen to be his own. Such an attitude can make the demands of the Mass and the Church’s public prayer a delight and the cause of joy, rather than a mere duty to be endured.

But there is no getting around the fact that the sacred liturgy is real work, a work that is required if we are to celebrate well as Christians. Both the Fourth Sunday of Advent and Christmas are days that must be celebrated due to their connection to the mystery of salvation. And if they both must be celebrated, then both must be marked by the work of love that is the Mass.

All of this to say that there is no “two-for-one” this year! No one single Mass satisfies the obligation of both the Fourth Sunday of Advent and Christmas Day. Christians should plan to join their brothers and sisters in the offering of the eucharistic sacrifice twice the weekend of Dec. 23, 24 and 25, whether this means once in the evening of Dec. 23, and then again in the evening of Dec. 24; or if it means once in the morning of Dec. 24 and once in the morning of Dec. 25; or if it means Sunday morning and Mass at midnight. Pace yourself, however; the work of the liturgy, which is the work of salvation, will demand something of you.

But, real love always will.

Father Erickson is the director of the Office of Worship for the Archdiocese of St. Paul and Minneapolis and pastor of Blessed Sacrament in St. Paul.