A CBS Olympics promo in the 1990s urged viewers to “Share a moment with the world.” In terms of release patterns on movies and, increasingly, TV shows, the question is how many of those moments ought to be shared simultaneously.

Folks in the U.K. have already shared an entire new season of “Downton Abbey,” the eagerly watched period drama, except for the final “Christmas episode.” Yanks, by contrast, will once again wait till January for the third arc of PBS’ “Masterpiece” to begin.

For Americans, this is a clear case of the shoe being on the other foot. Historically, U.S. movies and TV shows opened in North America first, gradually rolling out to other countries and territories.

Recently, however, that’s been changing, with revised schedules and rejiggered windows, as movies become a business driven by international box office. And while it’s not necessary for every TV show to day-date the world, perhaps, in an age of social media and online streaming that has in some vital respects made the Earth a smaller place — with opinions and spoilers ping-ponging back and forth across the globe — it’s difficult to justify staggering premieres.

A number of media observers have reached similar conclusions — particularly in Europe, where the blogs Monday Note and Zeitgeist and Stuff have both criticized lapses between release windows as archaic and frustrating to fans.

Just anecdotally, visiting friends in London several years ago found them hungrily watching “Lost” online, unwilling to wait for it to pop up locally. And as a U.S. TV critic, it’s increasingly common to hear from TV junkies abroad, seeking information about shows they’re eager to see, but which haven’t premiered yet on their home turf.

The TV biz — which has raced ahead of movies creatively in many respects over the past several years — has lagged behind on the issue of simultaneity, with some notable exceptions.

The poster child for global launches is surely “The Walking Dead,” AMC’s zombie hit. Fox Intl. Channels gambled by introducing the series at the same time in 120 countries via 200 channels, and has been rewarded with an international smash that’s, appropriately, a monster.

Although piracy was a concern for AMC, an even larger motivation for the strategy was to capitalize on the global conversations that can spring up around such a property, says Sharon Tal Yguado, exec VP of scripted programming and original development at Fox Intl. Channels. “We have a platform to create a TV event on a global level,” she adds.

There have been some other interesting experiments. Last year, for example, the BBC launched a new season of “Dr. Who” not only in the U.K., but also the U.S. and Canada.

For its part, PBS did consider moving the U.S. premiere of “Downton Abbey” into the fall (the only stipulation from ITV is the program must make its debut there first), but ultimately it decided to keep the launch date in January, where the show has performed so well, avoiding the crush of fall premieres on the commercial networks.

Again, not everything cries out for a global, day-date approach, and there’s a clear risk in the prospect of introducing a series that’s abruptly canceled by its U.S. network. Traditionally, there’s also been value in something establishing itself as a U.S. hit to heighten anticipation for its arrival overseas.

Once something becomes a success, though, there’s a strong case to be made for making it available all over, stoking not just a domestic groundswell but an international one. And as FIC’s Tal Yguado notes, there’s no measuring precisely what role the global drumbeat played in helping spur excitement for “Walking Dead” in the U.S.

Although a similar global pattern on Fox’s “Touch,” starring Kiefer Sutherland, hasn’t rivaled that success, Tal Yguado says her division is committed to bringing out at least two shows a year on a worldwide basis.

“You really need that viral show that comes with a fan base,” she says.

By definition, not everything qualifies as a “global event.” Eventually, though — and especially with certain kinds of serialized projects — the industry might have to consider a line the maids in “Downton” could never get away with using: “We don’t do windows.”