be as regular as clockwork

1. To happen at predictable intervals. My daughter starts crying every night at bedtime—it's as regular as clockwork. One thing I loved about living in Germany was that the trains were always regular as clockwork. If it's 8 PM, Dad is probably sitting in his armchair and reading the newspaper. It's an occurrence that's as regular as clockwork around here.

2. slang To have reliable, healthy bowel movements. I've been as regular as clockwork ever since I started eating a healthier balance of protein, fiber, and carbohydrates. I'm only as regular as clockwork because I drink all of this prune juice! Lately, I've been dealing with constipation. I miss the days when I was regular as clockwork.