I had a problem yesterday where I couldn't recall if I'd taken my slow release 80mg propanolol in the morning.

To be on the safe side I called two pharmacies and they both advised to wait until this morning before taking another dose. So I took it around 8:30am.

I'm a bit worried now because I usually take them around 11am.

That means if I DID take it yesterday, it's been around 20 hours between doses.
My meds say 'take one once a day'.

I was wondering if you have to wait exactly 24 hours or is it okay to give or take a few hours? I don't think I DID take any yesterday, but if I did do you think it's dangerous?