What time does McDonald's start serving breakfast

I feel like I wanna say as soon as they open which would be 5:00 a.m. I do believe?

I think that the drive thru starts at 5:00 am

At 5 am but for those open all night then some items all night long.

For the 24 hour locations, 3am....other locations locally 5:30am

I do believe Frenk here is correct