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Comment by em500 | Hacker News Reader

The theory is that tomatoes meant for canning can be harvested at a more optimal stage of ripeness (and they don't need to be bred for long shelf life) compared to fresh ones. I don't know if anyone has done any serious testing of the theory though.

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In Germany, and maybe other countries as well, the tomato cans have a 3 digit number printed on the bottom of the can. 220 for example. That's the canning date. The good ones, read Italian ones, usually also include a 2 letter code, like SA for Salerno, which indicates origin.

Obviously not a guarantee, but you can at least eliminate ones that were canned too early or too late depending on variety. Common advice is to pick the ones canned between 215 and 245 (Early August to early September) as that's the typical harvest time.

TIL!

I had to check and yes, the cans sold here (Switzerland) have the same code. Now I have a new hangup and that's buying those within the right range :)

I don't eat tomatoes, but... How does the date encoding work?

215 = August 245 = September

Is it just the day of the year?

I think so - the 215th day of the year is August 3.

What happens in leap years?

The 3rd of August probably becomes 216 so just add 1

yes - I thought of that but figured that it didn't matter for figuring out what tomatoes would be best.

It's such an interesting system I never even considered. Does this mean most of the tomatoes are all planted and harvested on roughly the same days? I thought it would've been like a farm by farm, rolling harvest kinda situation.

Depends on region and variety. Tomatoes on the same plant also don't ripen on the same day.

Yup.

For reference: https://www.epochconverter.com/days/2023

One other aspect is the tomatoes sold in supermarkets have to be varieties that can withstand some considerable time being trucked around, where as presumably the canning facilities are regional to the growers.

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