Any Intelligent Designer worth his salt could have done a better job designing a solar system for his favorite creature. I mean, what's this business of having the Earth spin on its axis 365.2422... times during a single journey around the Sun? A nice round number, like 365, would have made things hunky-dory. No need then for leap days.
But no. We have to go to all this silly business of adding a day to every year divisible by 4. Except not in century years. Except in those century years divisible by 400, such as 1600 and 2000. Which gives us 97 leap days every 400 years. Which averages out to 365.2425 days per year, which still isn't perfect, but close enough.
And while he was at it, a really intelligent Designer might have contrived a year of exactly 360 days. Now that's a nice round number, divisible by lots of factors, offering plenty of opportunities for interesting calendars. Even the Babylonians saw the advantages, which is why we divide circles into 360 degrees. A protractor is a model of the solar system that might have been. Twelve months of 30 days. Four 90-day seasons. Sixty 6-day weeks, 15 to a season. Forty-five 8-day weeks. The possibilities of tidy segmentation are endless.
What could he have been thinking, the Intelligent Designer? I suppose it was a test of sorts, not wanting to make it too easy for us, seeing if we could rise to the challenge. Well, we did. So there.