Not if you put enough lime into it...
But I would wait until about 6:15...how hard is it to mash some avocado with some garlic and lime and a little hot sauce?

If you must make it ahead, store it something narrow enough to let you cover the whole top with the lime or lemon juice. Don't mix it in until you're ready to serve it.
I agree, though, that it's better to wait. I don't like cold guacamole, and you would want to refrigerate it if you make it ahead. Have all the ingredients prepped and ready, and throw it together at the last minute.

Or, press some plastic wrap on top of it and refrigerate. It only browns where exposed to air.

As Christine says, it should be served at room temperature. So take it out of the fridge ahead of time to warm up or nuke it for 10 or 15 seconds.

Jim

Mix everything except the avocado and refrigerate, then just mask up the avo at the last minute.

"Mask"?? I think I mean "mash".... ;-o

I do it like Sushipup said. But I also put any leftovers in the fridge, and do like other folks say, cover with lemon juice and put saran wrap over it. Stays mostly green, but better fresh. You can make it somewhat in advance though, does not have to be within a 15 min. window. Not sure how long the window is, but I routinely make it 30 min. ahead or more. (Just not sure how much more, lol!) But I use a lot of vinegary homeade salsa in my guac.

I don't like lime or lemon juice in my guacamole, which is the reason I suggested pressing plastic wrap onto the surface of the guacamole (not just stretching it over the bowl). A layer of acidic juice on top of the guacamole will work in a similar way of course, if you want that flavor. I certainly would not stir in enough lemon juice to make it acid through and through and that is
unnecessary.

In any case, the surface of guacamole will discolor quite quickly if exposed to air. Giving it a good stir at serving time will freshen it up.

Jim

Well I used lots of lime, then pushed plastic wrap around the top, and it kept beautifully for 5 hours. It was a hit and got snarfed up quickly. Thanks everybody. I used to know what to do, but cooking for the last two years has been low on my priorities since we started raising grandbabies. Hope my memory comes back, LOL.
Sherry

I just saw this and it's too late for the op, but if you put the whole avocado seeds back into the avocado (as many as you have) it will keep the guacamole green for a LONG time.

I meant to write "back into the guacamole," not "back into the avocado."