Are we allowed to work today?

[Daniel]

So yesterday was the Feast of the Immaculate Conception, but I hear that on the new calendar the feast is celebrated today rather than yesterday (because, in the NO, the Second Sunday of Advent outranks the Feast of the Immaculate Conception, so the latter is transferred to the following day, i.e. to today).

Granting that the new calendar is binding, are we allowed to work today? And buy and sell?

I'm a little confused on how this rule works. I know that we aren't allowed to work or buy stuff on holy days of obligation, and I know that the Feast of the Immaculate Conception is a holy day of obligation. But I've heard that we are not obligated to attend Mass today, at least not in my diocese. So I guess today is not a holy day of obligation? (Or is it still a holy day of obligation, even though the obligation to attend Mass is done away with?)

[Gardener]

Yes, it's 9 Dec. For those who observe the TLM calendar, today is simply what it is.

For those who abide by the NO calendar, the obligation is not transferred with the Feast in the new calendar.

See page 8, item 9 in "Miscellaneous Notes":

Since December 8, 2019, is the Second Sunday of Advent, the Solemnity of the Immaculate Conception  of  the  Blessed  Virgin  Mary  is  transferred  to  Monday,  December 9,  2019.    The obligation to attend Mass, however, does not transfer.  The Optional Memorial of Saint Juan Diego Cuauhtlatoatzin, December 9, is omitted this year.

http://www.usccb.org/about/divine-worship/liturgical-calendar/upload/2019cal.pdf

If there is no obligation to attend Mass, there can be no obligation to Holy Day activities (or lack thereof).