Why do people use the phrase "24 hour timeframe"? Have you ever stopped to think about that exact statement and how it doesn't even make sense? A single hour is singular, so I could see saying a "one hour timeframe", but since there is more than one hour in 24 hours, shouldn't it technically be along the lines of a "24 hours timeframe"?
Of course this phenomenon isn't just with 24 hours. If you are explaining that the drive to visit your grandmother takes four hours, you would generally say "we are going to be taking a four hour car ride" instead of "we are going to be taking a four hours car ride". The second version may be technically correct, but the first one just seems to sound better.
Same holds true with other measurements of time as well. If you were going out to eat on a Saturday evening and the hostess told you there would be a wait time before you could be seated, I can promise you she would tell you that there is a "20 minute wait" instead of a "20 minutes wait", unless of course if she said "the wait time will be approximately 20 minutes", as I'm sure she wouldn't say "the wait time will be approximately 20 minute".
I equate this to the type of thing we hear and repeat without ever taking a few seconds to actually think about what we are saying. It is somewhat like when a person refers to the "Geneva Convention" when in reality what they mean to say is "Geneva Conventions". That might not have so much to do with English as it does with History however, so perhaps that isn't even the same issue.
What really boggles the mind however is how it seems to vary depending upon the specific terms used to describe the time. If you are taking about 30 seconds, you might say "there will be a 30 second delay" or "I only have 30 seconds before my alarm goes off" or "One half of a minute is 30 seconds", or even "we need a 30 second time interval between groups". You see - there is zero consistency here. Sometimes it is singular, other times it is plural and yet we automatically assume one is correct and the other incorrect depending upon context and context alone.
Sort of makes me wonder if the CBS news program shown on Sunday nights should be called "60 Minute" instead of "60 Minutes", but I suppose there is some special rule for trademarked names just like "50 Cent" should really be "50 Cents". I suppose discussing the half dollar rapper might have been more entertaining, but since when did rappers care about proper English?
In any case, I wonder if I'll ever be driving by a cafe at a late hour where I'll see a sign flickering in the window which says "Open 24 hour". Honestly it is a distinct possibility, but only because the "s" is burnt out.