Sure it may be a riddle but the wording really screwed it up for me or any proper person with an active conscience, Hello, it says IN the morning IN the afternoon and IN the evening. If it were to mean that a man's like were to be LIKE how a day goes, I would have only answered MAN to four legs in LIKE the morning, two in LIKE the afternoon. and three at LIKE the night but that's NOT how the question worded it! WTF when a baby grows up enough to be able to stand on two, that's like YEARS later, not just a few mere hours, damn who had smeared sphinx's true reputation? a baby is STILL A REAL BABY CRAWLING ON FOURS SLIGHTLY LATER IN THE AFTERNOON, I would not call that a teen/prime age. That's what anyone should see as a REAL principle. Not thinking the answer is going to be LIKE that of a MAN when in the FIRST place the question does not ASK for LIKE. It said it IS IN THE MORNING, then IN THE AFTERNOON, then AT NIGHT, not some fantasy imagining of some UNFORESEEN future by which we presumebly accept as definite, no. What if you don't know what will happen while the person is still 4 legs? Will they get minced by a machine, will they be amputated, will they gain chemical defects sprouting extra legs? No account and therefore you cant determine it will become 2 legs. Hence is I think the sphinx riddle should be more harder to figure out than this. Jeez these people....
Now, as to what my views on what the answer could be, as I have said down there I have agreed to Wingnut's answer down there because a dairy farmer really does fit into the more IMMEDIATE QUESTION SETTINGS. ok.
so.... I think another possible answer for the riddle is...Alcohol! When you have FOUR bottles (legs) of wine on a shelf in the cellar, you take off two to share with a friend reducing the amount in that shelf in your home to TWO bottles (legs), later on in the evening after you have finished the 2 bottles, either you or your friend or both had been not strong enough to handle the strength of the alcohol, you will end up prolly just arrived back home but puking right into some bucket or sink or toilet, well now even if the two of you combined you may prolly only just be puking back out up to about one bottle's worth of alcohol! Meaning now in your house there contains again about THREE bottles (LEGS, YES, LEGS) worth of Alcohol! Ain't that marvelous? In a logic kind of way....