The short version. Every coffee carries two dates. The roast date tells you how long ago the beans met heat. The harvest date tells you how long ago they left the tree, and almost nobody prints it. Green coffee holds its best for something like a year after harvest, then flattens and turns papery. Zambia picks from May to September, the opposite half of the year from Ethiopia, Colombia's main crop and Central America, so a Kasama bag roasted in Lusaka in November is a few months from the tree at the moment most northern-hemisphere origins are closing in on a year. Brazil shares our calendar, and we come back to that below.
Take a bag of washed Ethiopian coffee off a shelf in London or New York this December. It is probably a fine coffee. It was also, in all likelihood, picked the previous December or January, milled in February, on a ship in March and in a warehouse by May.
The bag will tell you when it was roasted. It will not tell you any of the rest.
The clock nobody prints
Green coffee is a seed, and seeds keep. That is why the trade can move coffee around the world by sea rather than by air. But keeping is not the same as standing still.
Importers describe a coffee's age in crop years: new crop, current crop, past crop. Sweet Maria's, who have sold green coffee to home roasters since the 1990s, keep a glossary for those terms and a rule of thumb behind them. As a general rule, they say, a coffee should be sold out within five or six months of landing in the United States.
Early shipments of Central Americans, machine-dried to get them to market quickly, can go flat in five months. Their own example is a 1998/99 Costa Rican Tarrazú, cupped in July, three months after it had sold out, and already fading. They also allow, fairly, that a properly stored coffee changes little in its first year and that most are fine for about eighteen months. Royal Coffee, a green importer in California, treats green coffee as a seasonal product with a finite shelf life, which is the same point made from the other coast.
Past the window, the descriptors are unflattering and consistent across every source we read: papery, woody, cardboard, straw, jute bag. Sweetness goes first, then acidity, then body. The coffee does not spoil. It fades.
The mechanism is slow chemistry rather than rot. Moisture drifts, lipids oxidise, and the aromatic precursors that roasting would have turned into fruit and caramel break down into simpler, duller compounds. A roaster can hide some of this behind a darker roast, and none of it comes back.
Coffee has two hemispheres
Coffee is picked in the dry season, and dry seasons fall on opposite sides of the year depending on which side of the equator the farm sits.
North of the equator, the big origins pick from roughly October to March. Ethiopia picks from October into January. Central America picks from November to March. Colombia's main crop comes off from October to December, with a smaller second crop, the mitaca, from April to June. Kenya's main crop is picked from October into January, with a smaller fly crop from May to July, on the seasonality guide published by the importer Mercanta.
South of the equator the calendar flips. Brazil picks from May to September, and so do Peru, Papua New Guinea and Zambia.
Add three to five months for processing, drying, resting in parchment, milling, paperwork and the ship, and you get the arrival calendar roasters plan around. Central Americans reach northern warehouses from about April to June. Ethiopians and Kenyans peak there from March to June. Brazil's new crop starts landing in July.
Now look at December from each origin's point of view. A washed Ethiopian roasted in December is eleven or twelve months off the tree. A Guatemalan is nine to twelve. A Colombian could be new or a year old depending on which harvest the roaster bought. A Zambian is three to six.
Here is the fair caveat, and it belongs before the argument, not after it. Brazil, the largest producer on earth, shares our harvest months, so in December a good Brazilian is as fresh from the tree as a Zambian. The difference is what people buy each origin for. Brazil is bought for chocolate and body. The origins specialty drinkers chase for acidity and fruit, the ones whose brightness fades first as green coffee ages, are exactly the ones that are oldest on a northern shelf in the northern winter.
The Zambian calendar
Zambia's arabica is picked from May through September, with most of the picking between June and August. Specialty lots from the Kasama estates typically ship between June and August, according to Omwani's Zambia sourcing guide, which advises roasters to start talking to the estates in March if they want them.
We roast in Lusaka, about 850 kilometres by road from the estates, so the coffee does not cross an ocean before it meets the drum.
Which means that in the last quarter of the year, when northern shelves are holding the oldest coffee they will hold all year, ours is the closest to harvest it will ever be. That is the case for the December gift bag, and it is a chemistry argument before it is a marketing one.
The second clock
The roast date matters too, and this is the one the specialty world has spent twenty years teaching people to read.
Roasting fills the bean with carbon dioxide. For the first days the gas leaves quickly, and coffee brewed inside that window tastes thin and sharp because the gas gets in the way of extraction. Most of the trade now puts the sweet spot somewhere between four and fourteen days after roasting; Clive Coffee, an espresso-equipment house in Portland, Oregon, rests both its filter coffees and its espressos at least seven days before pouring them. Lighter roasts want longer. Espresso wants longer than filter. Darker roasts peak sooner and fade sooner.
After the peak, oxygen does its work. Whole beans in a sealed bag with a one-way valve hold well for weeks. Once the bag is open, three to four weeks is a fair limit. Grinding speeds everything up. Freezing, airtight and never refrozen, all but stops the clock: the roasting consultant Scott Rao has written that vacuum-sealed frozen beans would take months or years to reach the state a room-temperature bag reaches in a week or two.
Supermarket coffee runs on a different clock entirely. A best-before date, often a year or more away, tells you nothing about when the beans were roasted. Most of what sits on a Lusaka supermarket shelf was roasted somewhere else, and the bag will not tell you when.
How to read a bag
Roast date: it should be printed as a date. If there is only a best-before, subtract at least a year.
Harvest or crop year: rare, but a roaster who prints it is telling you they know. A northern-hemisphere bag marked "2025 harvest" and bought in late 2026 is past crop.
Origin: once you know the two calendars, the origin tells you the harvest month within a few weeks.
Where it was roasted: coffee roasted at origin skipped the ocean. That is not a quality guarantee on its own, since roasting is a craft wherever it happens, but it removes one long, warm leg from the green coffee's life.
What we print, and what we don't
I went back to our own 1 kg bag while writing this. The front panel carries the variety, the altitude, the cupping score and the name of the man who roasted it. It carries no date of either kind. We roast after you order and ship within two days, so the roast date is, in practice, the week you ordered. But "in practice" is not a printed number, and I have spent this whole piece arguing for printed numbers.
The fix is cheap: a roast date stamped on every bag, and the harvest window beside it. The second costs nothing to print, and it is the number that tells you the most. I would rather the bag said it than I did.
Taste the calendar.
Shop the Zambian single origin
More from this series: Kasama, the town that grows nearly all of Zambia's coffee, what "low acid coffee" really means, and how we roast.
Frequently asked questions
How long does green coffee stay fresh? Roughly six to twelve months after harvest under good storage, and usable for longer. After about a year, sweetness and acidity fade and papery or woody flavours appear.
When is Zambian coffee harvested? May to September, with most of the picking between June and August. This is the southern-hemisphere calendar, shared with Brazil and Peru.
Is fresher always better for roasted coffee? No. Coffee needs about four to fourteen days after roasting to release carbon dioxide before it brews properly. Very fresh coffee can taste thin and sharp.
Why don't roasters print harvest dates? Partly habit, partly because many roasters buy through importers and do not track the harvest month, and partly because a printed harvest date makes an old coffee harder to sell.
Sources
Sweet Maria's Coffee Library, "Green Coffee Freshness: How Old is Too Old?" and the glossary entries "Past Crop" and "Harvest Crop". Royal Coffee, "How Long Do Green Coffee Beans Last?". Mercanta, "Coffee Seasonality". JayArr Coffee, "Coffee Harvest Calendar", May 2026. Omwani, "Zambia Coffee Production & Sourcing Guide", April 2023, and "Zambia Speciality Coffee". Scott Rao, "Resting Roasts: Is Fresher Better?". Clive Coffee, "Is Your Coffee Too Fresh?". Methodical Coffee, "Freshly Roasted Coffee, Explained: Degassing, Rest, and Flavor".