How To Round Unixtime To Midnight

This might be pretty obvious to anyone with basic math skills. It took me a few minutes to figure out, so I thought I’d share with the world. To round a unix timestamp to the previous midnight (UTC) use the following function:

function unixtime_round_to_midnight ($t) {
return $t – ($t%86400);

Thanks to Ian for pointing out my math ineptitude.