ab und zu is maybe the best way in German to say every now and then.
- “Wie oft gehst du in die Sauna?”
“Oh, ab und zu.”
- “How often do you go to Sauna?”
“Oh, every now and then.”
Why is it ab und zu?
I have no clue. I don’t think there is logic™ to it.
But absolutely do add it to your vocabulary. It’s one of those things that’ll make you sound like a native speaker.
Oh by the way:
Alternatives are hin und wieder and dann und wann. But ab und zu is by far the bestest.