I can't speak for the USCCB, but it is almost always preferred to follow the normal Lectionary cycle on optional memorials, even if you are celebrating that memorial. Unless your parish has a particular devotion to St. Joseph the Worker, I'd use the readings of the day.

For example, May 1st is the memorial of St. Joseph the worker. On the usccb calendar for this year, the readings posted are for Thursday of the second week of easter: http://bit.ly/NVmhg7

But on May 1st in 2003, they chose the readings for the memorial of St. Joseph: http://bit.ly/1fkyv9u

Sienal, did you even look at the readings listed for those two days? Try examining the specific readings chosen in each of those cases, and then I think you'll be able to come back and explain to us why the USCCB did what it did.

Siena,

Now that I've considered your posting in greater depth and "compared" the readings as Mark suggested, I think you ask a very good question. Based on the info Fr. Krisman gave in this thread, I checked and the Gospel for the Memorial of Saint Joseph the Worker [559] on May 1st is Proper: Matthew 13:54-58.

I see that on the 2003 page you sent, the Gospel is John 3:31-36 even though the page says "Memorial of Saint Joseph the Worker." So you have piqued my curiosity, too. You might need to call the USCCB about that unless someone else can explain the information you found.

Mr. Thompson,
I believe you are referring to how those readings happen to be the same. But it still makes a difference which feast is celebrated. In this case their antiphons are different.

The entrance antiphon for Thursday after the 2nd Sunday of Easter is taken from Ps 68 (67): 8-9, 20:

O God, when you went forth before your people,
marching with them and living among them,
the earth trembled, heavens poured down rain, alleluia.

The entrance chant for St. Joseph the Worker is Ps 128 (127): 1-2:

Blessed are all who fear the Lord and walk in his ways!
By the labor of your hands you shall eat;
blessed are you, and blessed will you be, alleluia.

Another question: on that day could I use the entrance antiphon and readings from the St. Joseph feast and the responsorial psalm and communion from the other feast?

As a general rule for ordinary time:

1. Solemnities
2. Feasts
3. Sundays of Ordinary Time
4. Memorials
5a. Optional Memorials
5b. Ferias

In the case of Optional Memorials and Ferias, they are generally considered equal and it is up to the celebrant to decide which they will celebrate. Many places in general tend to omit optional memorials unless there is a particular local devotion to a Saint.

This year, we see a number of feasts and Solemnities fall on a Sunday, which include The Presentation of Our Lord (Candlemas), the Solemnity of Sts Peter and Paul and the Commemoration of All Souls.

It gets a little more complex for the other seasons, but in general:

A.) Absolutely nothing trumps Holy Week and The Easter Octave.
Last year the Solemnity of the Annunciation was moved to the Monday after the Easter Octave as March 25th fell during Holy Week.

B.) Nothing trumps Christmas and it's Octave.
It can get a little complicated, as the Sunday after Christmas is The Feast of the Holy Family, which can end up trumping St Stephen's Day, St John the Apostle's Day, the Feast of the Holy Innocents, etc.

C.) Epiphany on January 6th takes precedence, unless in your local calendar it has been moved to the Sunday between the 2nd and 8th of January - ie Epiphany Sunday instead of Epiphany on Jan 6th

D.) All Saint's Day and All Soul's Day take precedence over Sundays of Ordinary Time, although in the 1962 calendar, All Soul's Day is moved to Monday if Nov 2nd is a Sunday.

I am uncertain as to the precedence of the weekdays of Lent and Advent, but I am given to understand that in most places, St Patrick's Day is only an optional memorial and is generally trumped by Lent. (St Patrick's Day is a Solemnity in Australia, so it takes precedence.)

Isn't "Feast" as distinct from "Solemnity" now understood as a feast ranking lower than Sundays?

Good question. Not necessarily. Major feasts of the Lord and the Blessed Virgin Mary still replace Sundays.

I'm still a little confused at whether the non-solemnity Feast of the Lord is a thing.

^^Transfiguration (August 6)

Also, I'm not sure if the Dedication of the Lateran Basilica is really a Feast of the Lord, or if it just enjoys special place in all the Churches of the world, like the dedication of your more local cathedral. I'll have to look that up.

Feasts also typically only have one reading unless they fall on a Sunday, like other weekday Masses.