DS1307 accuracy

[mackrackit]

I use on average a couple of thousand DS1307's annually. If it's better than 15 minutes per year (and that's matching it exactly with a 12.5pF xtal), you've got a good one. For the money you pay (say around $0.75 in quantity) they are totally rubbish.

I keep meaning to program up a 18F part with a secondary 32kHz xtal and have a background interrupt timekeeping program... finally consign the 1307 to anals (deliberate spelling) of History.

That is interesting. I only use around ten per year so I do not have the kind of data you do, but I typically see errors less than a minute per six months.

Maybe the built in crystal in the DS1337C is better???