Using the 's after a name denotes posession. Jones is the name. The Jones's dog is their posession. Unless your referring to keeping up with the "Joneses" which denotes more than one Jones family.

What? When??! You weren't watching CNN on Wednesday, April 19, 1995, at 11:15 Central Daylight Time? You mean, you didn't see the big announcement? Oh, it was really something. After months of what can only be described as a grammatical version of the legendary Battle of San Juan Capistrano, the head of a group whose motto was, "Get your Eses Moving!" - ironically, a fellow named Jones - announced that he and Williams, the opposition leader, had reached a compromise that both sides could handle. Jones announced it was OK, officially, to use another "s" after a name that already ends in "s". Various members of the Jones family disliked the one "s" limit, and therein lies the rub. "Every name that ends in a different letter gets a new 's' when its owner acquires something. Why can't we get a new 's' too? So what if we have an existing 's'? Unfair!" they whined. The Williams', or Williams's, contention, or the contention of the Williams, was that one "s" had worked for eons. Why shake things up? Besides, if the idea caught on, the Jones' new "s's" would bring in a new breed of Apostrophe - and a whole new batch of trouble. The concern was valid. Common knowledge in those days knew Apostrophes itched to break free from the rules that governed the lives of punctuation marks everywhere. Apostrophes were a social group, and enjoyed hanging out with the 's' crowd whenever and wherever they wanted. Imagine the effect's' of 's'uch a departure from the 's'tatu's' quo. You may not be aware that Apostrophes and Commas are related. Granted, it's been years since they acknowledged their kinship, but look closely and you'll see the resemblance. Whatever you may have heard on the matter is likely more fiction than fact - for example, that tall tale about Apostrophes descending from Commas. Ridiculous! A quick look at a few sentences proves that story wrong. Anyone can see that Apostrophes ascended. Honestly, some people will believe ANYTHING. The following is what I like to call "the true history". "Is it really true?" you ask? Are you serious? How would I know? But who would believe me if I called it "the fake history?!" What a question.<snort> Credibility matters. Back in the day, the Comma Family, ruler of all things grammatacational, was comprised of two branches. Members of the stuffy, main-line Comma Family branch were known as the Patriarchs of Punctuation. They founded Sentence Services and oversaw the entire Traffic Division. Rules, structure, and convention were paramount. The other Comma Family branch members were fun, lively, and usually in trouble. When a Comma showed up inside a racy headline, nobody asked, "Hey! Where'd that Comma come from?" Everyone just knew. The two branches coexisted for years - while not always in harmony, peacefully enough. But as we all know, a house divided, eventually falls. This particular tumble began when one of the livelier Commas stormed off his page after taking an unexpected undercut punch from a lower case q, searching for his lost u. Whack!! Up through the baseline, right at the Comma's tail. Ouch!! Talk about unnerving! And on a tough assignment, too - keeping order among those high-strung adjectives. Unfortunately, we never found out exactly what happened. The first eyewitness, Scared, freaked out and ran away. The second, Worried, concerned about his pal, followed. In all the commotion, no one interviewed the third and possibly best witness, the sentence - the host, for Pete's sake! What a shame. Even then, sentences made outstanding statements. Next thing you knew, the Comma (a rapid healer) was living it up, and get this - partying with a bunch of Contractions - the black sheep of the grammar world. That was the deal-breaker - and the start of complete disruption in Language Land. For a Comma, even an adventurous one, it was tantamount to sleeping with the enemy. Imagine the reactions of shock and outrage at Comma Compound. Rumors had our frisky renegade swinging around on "T"s and "S's like the alphabet was a jungle, and he was Tarzan. He even ran around with those LL twins, the ones who headlined in "YOU'LL..." and the sequel, "WE'LL...". (That's him up there, with the starlets. No wonder he's grinning, eh?) The main-line Commas quickly disowned the flamboyant little high-flyer. Most of the more liberal branch members reacted by disowning themselves. Sub-branches of French and Greek Commas joined the rebellion and discovered they liked the high life, so to speak. Others joined soon after. They began calling themselves Apostrophes, and gave up living on the baseline. They became famous after some of the wealthier members found Contractions on sale and bought every one. Under the Apostrophe's tutelage, Contractions shaped up. Apostrophes were wild, sure, but don't forget, they had centuries of elegance and good taste as Commas under their belts and in their genes. The pupils soon looked and sounded better. When they hit the streets with their mentors, they found acceptance, even popularity. The stuffy Commas resented the attention, and the changes. The ill feelings grew sicker when a Contraction sweet-talked the head of the Possessives Dept. into allowing Apostrophes a piece of that action. Meanwhile, some main-line Commas and a few Apostrophes, including the little hellion who started the whole thing, secretly forged an alliance called, "The Comma-Postrophe's". Despite raised eyebrows, the two-for-one approach was a big hit. Last I heard, they caught a long-running gig in Vegas and never looked back. Fast forward to 1994. A Mr. Williams, no doubt hired by the Comma family, began talk of making "One Owner, One Apostrophe, One S" the official rule. Here came Mr. Jones, outraged by the idea. He thought the members of the Jones family, and anyone else, should be able to stick an "s" at name's end. The Commas and their supporters espoused less complexity - "S is for Simplicity, not S'Stupidity". Jones called on the Apostrophes, and wouldn't you just know it? Those rascals couldn't wait to shake up the punctuation world again. Confusion was the strategy, and it worked. "Is it the "S" thing, or what?" people wondered. The literary world felt an immediate impact. Nothing - no billboards, magazines, signs, or newspapers - carried a full complement of punctuation. Some unruly marks missed assignments, or showed up wh/en and};" {where # they, $# liked). Imagine. Others persevered, as did the 26 Alphabetites. Even the 5.5 members of the elite Vowels Corps supported the cause with a more consonant-friendly attitude. What can I say? I don't make this stuff up, you know. The anarchy affected TV, too. I remember watching Wheel of Fortune one night when a band of Asterisks, demanding wild card status, seized control. Pat Sajak fainted after two insurgents commandeered the Phrase Board and loaded it with obscene messages about Vanna White's supposed dalliance with the Percent Sign. CBS even yanked the Y & R off the daytime lineup, fearing the two letters would grab the Ampersand and flee Genoa City. When Campbell's Soup refused to accept alphabetic pasta, kids rejected Campbell's Soup. Parents and babysitters turned to Spaghetti-O's and hoped for the best. Erasers disappeared almost overnight. With a little luck and some green, though, you could usually score some black market white-out. A quick-thinking guard at LAX detained a man when she noticed his suitcase had been refitted with two industrial strength padlocks and and a galvanized steel chain. Police forced it open, and found over twenty-five stolen Harbrace College Handbooks and a one-way ticket to Rio. Dots, laboring for centuries as the stop signs on sentences, discovered their true nature and began traveling. The members of one group met tragedy head-on while attempting to disguise themselves as a gang of rebellious colons. They'd missed the finer points on effecting the difficult two-story stance, and the top dots rolled off. The lead roller panicked and spun himself onto a Weekly World News. The other dots followed and BAM! BAM! Thousands of stomping exclamation points flattened the entire group. The points claimed self-defense against a much-feared and long-awaited alien invasion. You've probably seen this shocking photo, taken a split second before stompage: !!!!! !!! !!!!!!!!!!! !! !!! ! Sometimes only the thinnest of veneers separates civility from savagery. Fortunately, the erosion of this particular veneer shocked the Powers that Were at Grammar HQ into taking control and restoring peace. In 1995, the two sides settled the dispute. The Williams gave up on the one "s" idea, and the Jones agreed not to involve Apostrophes. Other points were made, and taken, of course, but that's another story. Language appears to have weathered the storm. To address your comment on the first answer, I believe you can thank the Jones family itself for the change. Who knows the reason and rhyme? They like "s's" is my guesses. If you have any questions, please email me. I can always come up with more. ~~~~~~~~~~~~~ OK - here's the straight, no-kidding answer: In his classic and much referenced grammar book, The Elements of Style (1918), William Strunk's instruction is to: "Form the possessive singular of nouns with 's." He gives the following examples: "Charles's friend" and "Burns's poems". He continues, "Exceptions are the possessives of ancient proper names in -es and -is, the possessive Jesus', and such forms as for conscience' sake, for righteousness' sake." (I added the last part because it seemed somewhat relevant and may help in the overall understanding.) http://www.crockford.com/wrrrld/style2.html#1 Strunk, in 1918, roughly, stated that an "apostrophe s" tacked onto a word that already ends in s showed proper form. I found a more understandable explanation in "The Grammar and Style Guide", by Laurent Grenier. http://www.laurentgrenier.com/grammar&style.html The following is a brief excerpt: "Errors are common when the name ends in s. Curtis's house is correct, meaning a house owned or occupied by someone named Curtis; so is Curtis' house if the writer prefers not to add an s in such cases. Problems start when the Curtis family is involved. More often than not one sees the Curtis's house, which is wrong. The plural of the surname Curtis is Curtises, so it must be the Curtises' house. Similarly Jones, Jones's house, the Joneses' house; Mr. Cross, Mr. Cross's house, the Crosses' house. I think errors are usually the result of a hazy understanding of how to make names plural." Jones's seems to have always been the preferred spelling. In your question, however, Jones's is correct for one Jones, as in one family. If several Joneses were involved, then the possessive would be Joneses' As an answer to the question you asked, since The Elements of Style is a standard definitive work on English grammar, it was okay as of 1918. I doubt Strunk invented the rule, so I assume said rule was alive, well, and in use long before 1918. You wanted to find out when the rule shifted. As far as I know, no shift took place.

O my AB brethren and sistren, I'm going to post a response to this oldish Q because Jodie44's exquisite rant won't have been seen by any newbies. Read it and fall on your ess's laughing.