Jewish holidays begin at sundown the night before, because the Jewish ceremonial day runs from sundown to sundown. Most gentiles these days are pretty good at being aware of Hanukkah, Passover, and at least some of the High Holy Days. And I appreciate that.
Scheduling a concert at which (specific) you expect me to be present on the day of Erev Pesach (which begins at sundown on April 19 this year) is Not Cool. When I e-mail you to alert you to this, it is even Less Cool to say "oh, no, that doesn't conflict with Passover. Passover begins on the 20th!" Here's a hint: If your calendar says, on the 20th, "Passover begins today," it is not the value of "today" that you assume it is. That is a goyische calendar. If your calendar makes no mention of sundown, then you cannot assume that your calendar is telling you the whole truth. Look it up -- this takes all of two seconds to Google. By 2008, Judaism should not be so exotic a concept that this should come as news to you.
Especially if you know enough about Judaism to have wished me "Good Yuntiff" at Passover last year.
I know it sucks, but it's a fact of life. There are foods that people will not eat. There are foods that people are allergic to. And vegetarians exist. It is reasonable to assume, in this day and age, in a major city such as New York or Chicago, that a good proportion of the guests at your gathering will come with some of these little food caveats.
Obviously, you can't cater to everyone's food issues, but perhaps it's not so unreasonable to make sure that you avoid the major, most well-known ones. Lots of people are vegetarians. Many people won't eat pork for various reasons, and shellfish are a major, well-known food allergy. These shouldn't be too difficult to deal with.
So then why, specific otherwise-very-nice couple, do you host an elegant gathering in New York and serve lovely, tempting, fresh from the stove hors d'oeurves . . . none of which are vegetarian, half of which feature either shrimp, ham, or both, and all the while, your feature presentation is an assemble-it-yourself Thai appetizer featuring dried shrimp and a shrimp-based sauce that completes the dish?
I know that you like cooking Southeast Asian food, and that you're proud of your ability to do so. But really, is chicken satay that hard to do? There are so many lovely vegetarian foods to be found in Southeast Asia -- why go for precisely the ones that set off the most common food issues? (Although your duck hot pockets were very tasty.)
In summation: Think about the world, dudes and dudettes, for just a moment before you act.
That is all.