RSVP
This little acronym gets thrown around a lot. Often, it is used (not utilized, ahem); sometimes, it is abused. Let’s investigate.
RSVP stands for repondez s’il vous plait, meaning respond if you please. It is the French way of someone politely asking you to contact him or her in order to indicate whether you will be able to attend whatever event he or she sent you an invitation for. NOTE: The acronym does not call for periods, despite what some calligraphers deem necessary for high style.

High-style RSVP, with unnecessary periods
Let’s say that your friend Frankie mailed you an invitation to her son’s birthday party. The invitation has RSVP printed in bold letters, with a telephone number and e-mail address below it. The polite (and expected) thing to do, as soon as you receive the invitation, is to check your availability and immediately call or e-mail Frankie to let her know that you can or can’t make it to the party. If you two regularly contact each other some other way, such as tweeting or texting, that would probably be fine, as long as you verify that she received your message; but since the invitation listed a telephone number and e-mail address, one of those options would have less chance of somehow not getting your RSVP to her. It’s your call — just verify.
The purpose of the RSVP, by the way, is to help the person hosting the event to plan said event more efficiently. If 30 invitations are sent out (with 30 invitees) with no RSVP, then the host is assuming that 30 guests will arrive; the host will have to prepare to adequately serve 30 guests, plus the host and any of the host’s helpers or family.
But if an RSVP is on the invitation, the host’s hope is that if not everyone can make it and if those folks notify the host by the requested date, the host will be able to adjust the event requirements in time to save money and supplies. So, for example, Frankie could plan on buying a smaller cake and fewer jugs of fruit punch because seven invited guests replied that they could not come to the party, while 23 guests replied that they would be there, with bells on. And in these interesting economic times (yeah, you try to avoid that phrase these days), saving a few bucks here and there is a very good thing.
So please, folks, follow RSVP protocol and RSVP on or before the deadline on the invitation. If you’re a friend of the host (and you presumably are, or else why are you getting an invitation?), help him or her out and say that you’ll either be there or you can’t come.
One other thing: Don’t write, “Please RSVP by xyz.” The please is redundant.
One last thing: Don’t write, “RSVP in advance.” Duh — you’re expecting them to tell you they’ll be there after the shindig’s over?
Happy trails!
SAK
Tags: invitation, RSVP

I am not sure you used “allotted” in the proper context. I don’t think you allot a deadline – you set a deadline. You allot days or time to complete the task by the deadline. Allotted could have been deleted in that sentence and it would work, wouldn’t it?
Remind me again about dangling prepositions – is it acceptable but betrays a lack of creative writing or is it altogether incorrect?
“Allotted” is now “on or before the.” Good catch. Just deleting “allotted” would not have made the sentence clear, though.
Dangling prepositions: In the world of advertising, it is not only acceptable, but encouraged, as its corrected versions (e.g., “of which” and “for whom”) draw the ire of the creatives. In the halls of academe, they are still treated as the plague. In the real world (whatever that is), they are acceptable in limited quantities. And no, they don’t necessarily “betray a lack of creative writing.”