How does it work? How does SSPX celebrate Mass Divine Mercy Mass? It is a new mass. Does SSPX do a mix and match thing by celebrating the modern feast day but saying Mass from the 1962 missal?

I have attended SSPX, FSSP & some Independent Masses for years and none ever celebrated Divine Mercy Sunday. In fact, there are no Propers for such a Mass in the TLM Ordo....

I have attended SSPX, FSSP & some Independent Masses for years and none ever celebrated Divine Mercy Sunday. In fact, there are no Propers for such a Mass in the TLM Ordo....

SSPX does not currently offer a Mass of Divine Mercy. There are no propers in the Missal of 1962. What will happen when the Vatican issues the new "EF" missal?
 
There are propers for the NO Mass of Divine Mercy Sunday. They are the propers of the mass that is said on that day which is the feast of Divine Mercy "for the entire Church.” JPII decreed that the same propers were to be said  as were said before on that day.

This explains some of the situation :

The essential celebration of Divine Mercy Sunday consists in the celebration of the liturgy of the Second Sunday of Easter, during which the homily should focus on the scriptural readings of the day. It should be noted that the three cycles of scriptural readings and liturgical prayers are all centered on the forgiveness of sins and God’s infinite mercy, which endures forever.
In addition, it is necessary that the day publicly be called by its proper name, “Divine Mercy Sunday.” The Decree of the Congregation for Divine Worship and the Discipline of the Sacraments of May 5, 2000, which added this title to the Second Sunday of Easter, did not intend to leave this as an optional title. The Latin of the original decree literally states that “in the Roman Missal, after the title ‘Second Sunday of Easter,’ there shall henceforth be added the appellation ‘that is, Divine Mercy Sunday.’ ” Unfortunately, the English version in official use translates the phrase ambiguously: “or Divine Mercy Sunday.” But the Latin is clear: “seu,” in other words, “namely,” or “that is.” Moreover, this was the Holy Father’s intention in granting this title to the Octave Day of Easter; it is clear from his own public announcement during the homily for St. Faustina’s canonization, when he stated: “It is important then that we accept the whole message that comes to us from the word of God on this Second Sunday of Easter, which from now on throughout the Church will be called ‘Divine Mercy Sunday.’ ” In his Regina Caeli
address on Divine Mercy Sunday, 2001, the Holy Father thanked God that he was able  “to proclaim the Second Sunday of Easter as the feast of Divine Mercy for the entire Church.”
 Taken from “Understanding Divine Mercy Sunday” by the John Paul II Institute of Divine Mercy 2003

I've never heard of an SSPX chapel celebrating "Divine Mercy Sunday" either.  Where did you see this?  If I remember rightly, "Divine Mercy Sunday" is celebrated in the Novus Ordo on the Sunday after Easter.

Again, where did you see this?

Apologies; I was not clear. I did not mean to say I’ve heard that SSPX offer a Divine Mercy Mass. I know they offer Mass of Low Sunday, commonly from 1962 missal. There is no Divine Mercy Mass in the 1962 Missal. Although It will probably be called Mass for Divine Mercy Sunday in the new EF missal due out soon.

There is also no Mass in the NO composed especially as a Divine Mercy Mass. The NO priests celebrate the NOM Mess of the Sunday after Easter.
What I meant was that I have heard  that SSPX call Low Sunday “Divine Mercy Sunday” at least in some places and celebrate or categorize that Sunday as “Divine Mercy Sunday”, while saying the Mass of Low Sunday. I have also heard that they celebrate NO canonizations in some cases and in some places.
I saw this online after the OP here. “Our SSPX chapel had announcements at both Masses reminding the faithful it was Divine Mercy Sunday.”   forums.catholic/showthread?t=446657&page=5

Sorry for any confusion caused on my part.What I originally meant was does SSPX generally recognize the Sunday after Easter to be Divine Mercy Sunday? Is it Divine Mercy Sunday in SSPX calendars or Ordos of they produce Ordos?

This OP sounds like a wind-up.