Chances are, you feel guilty about it already, but here it comes: While 93 percent of us believe breakfast is the most important meal of the day, 56 percent of us skip it. Why? Well, chances are you know the answer to that, too: We’re really busy. In fact, according to NPD Group, Americans spend 13 minutes each day eating breakfast. (Another estimate puts that time at a mere six minutes.) Of course, brands like Kellogg’s are well aware of the situation. The challenge for most any breakfast brand lay not so much in convincing consumers that the product is tasty, but that it’s convenient and nutritious enough simply to make time for.

What’s interesting is just how long that proposition has held true. In fact, as the two ads here show, while Kellogg’s breakfast products have changed with the times, the essential selling proposition has stayed pretty much constant. “Both of these ads recognize the time-starved nature of the American family,” said Katherine Wintsch, founder and CEO of marketing communications firm The Mom Complex. “They recognize that breakfast is a means to an end—that the goal is to be fed.”

That was certainly the case in 1943 when this ad for Kellogg’s Corn Flakes appeared in the magazines of America. With the war on, 37 percent of American women had taken jobs in factories. Not that their jobs freed them from the obligations of taking care of the kids, of course. The result was a window for breakfast every bit as small as today’s. Kellogg’s responded to this reality with a shrewd message, pointing out that Corn Flakes was mainly a time-saver (mentioned in three different places in this ad), even as it offered the correlative benefits of nutrition and usefulness in preparing other meals.

“They were saying they were a partner in your busy routine,” said Wintsch. (Full disclosure: Her company’s clients include Kellogg’s, but on the retail-operations side, not advertising.) “They also didn’t have mom in a patronizing role—with the perfect coif, looking lovingly over her child—and offered tips and tricks on preparing other foods. It’s very selfless, which for that time was very modern.”

Kellogg’s has kept it modern, too, with last year’s rollout of its To Go breakfast in a bottle. While the spatial configuration of this November 2013 ad lacks the domestic setting of its earlier counterpart, its core message remains unchanged: We know you’ve got no time to eat breakfast, so try this. Here too, the nutritional message is central, but it takes a place behind the primary thesis of speed and convenience. “The underlying theme is that you have stuff to do and places to go,” Wintsch said. “Kellogg’s is just helping you get there.”

Just like it did 71 years ago. Funny thing, though: America figured out how to win a world war but still can’t figure out how to find time to eat breakfast.