Gestation and hatch date calculator
When is my cow, goat, ewe, sow, mare or doe due, and when will my eggs hatch?
Showing for United States
Source
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- Earliest due date
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- Latest due date
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- Due date for the last day bred
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- Days used
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- Shortest in the source's range (days)
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- Longest in the source's range (days)
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- Source
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Your vet's dates come first. These are planning dates from published averages; animals give birth either side of them.
The day bred, or the day the eggs were set, counts as day 0.
Where the source gives only a range, you see the window, not a single date.
Source
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- Earliest hatch date
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- Latest hatch date
- —
- Days used
- —
- Shortest in the source's range (days)
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- Longest in the source's range (days)
- —
- Source
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Hatch times vary with how eggs were stored and how the incubator is run. Watch from a few days before.
The day bred, or the day the eggs were set, counts as day 0.
Where the source gives only a range, you see the window, not a single date.
Date
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Your vet's dates come first. These are planning dates from published averages; animals give birth either side of them.
The day bred, or the day the eggs were set, counts as day 0.
Enter your numbers to see the result.
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1. Copy this address
2. Add it to your AI app
Claude (claude.ai and the Claude desktop app)
- Open Customize, then Connectors.
- Press + Add, then Add custom connector.
- Name it TallyTill calculators, paste the address and press Continue.
- Under Authentication choose No sign in, then press Add.
- In a new chat, press + at the bottom left, choose Connectors and switch TallyTill calculators on.
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ChatGPT
- In Settings, turn on Developer mode. OpenAI moves this switch from time to time; it is usually with the settings for apps and connectors.
- Add a new connector (ChatGPT may call it an app), paste the address and choose No authentication.
- In a new chat, choose TallyTill from the tools menu, or type @ and pick it.
Not every ChatGPT plan lets you add your own connector. If you cannot find the option, your plan may not include it.
Using another AI app? Look in its settings for MCP, add the address as a remote server, and choose no sign-in.
3. Ask your question
Say "use TallyTill", so the AI uses the calculator instead of doing the sum itself. For example:
"Use TallyTill: When is my cow, goat, ewe, sow, mare or doe due, and when will my eggs hatch?"
What you will see
- The calculator opens in the chat with the numbers you gave already filled in. Change any number and the answer updates.
- If a number is missing, the box is highlighted, or the AI asks you for it in plain words.
- The answer links back to this page, so you can check the working.
- The first time, your AI app asks if it may use TallyTill. Choose Allow.
The calculators take numbers only. They never ask for your name, your email or a password.
How this is worked out
The day bred, or the day the eggs were set, is day 0. The due date is that day plus the typical number of days the source gives, and the window runs from the shortest to the longest it gives. Where a source gives only a range, the calculator shows the window and no single date. With a breeding season, the first due date is from the first day and the last from the last day. Days used, and where they come from: cattle 283 (279 to 287), University of Nebraska–Lincoln Beef, beef.unl.edu/faq/pregnant-cows. Goat 149 (145 to 155), Penn State Extension, Dairy Goat Production, 2022. Sheep, meat breeds 144 to 147 and wool breeds 148 to 151, Penn State Extension, So You Want to Raise Sheep or Goats?, 2021. Pig 114, Purdue Extension VA-30-W, 2021, with 110 to 117 from Penn State Extension, Raising Pigs 1: Farrowing. Horse 340 (315 to 365), Purdue Extension VA-26-W, 2020. Rabbit 31 (28 to 35), Oregon State University Extension EC 1655, 2018. Eggs: chicken 21, turkey 28, most ducks 28, Coturnix quail 17, bobwhite quail 23, Mississippi State University Extension, Incubation Duration Periods; Muscovy duck 35 to 37, University of Missouri Extension G8353, 2017.
A worked example
Example dates only; use your own. A cow bred on 1 April 2026 is due 283 days later, on Saturday 9 January 2027, and could calve from Tuesday 5 to Wednesday 13 January. Chicken eggs set on 1 March 2027 hatch 21 days later, on Monday 22 March. If your vet gives 42 days from 18 October 2026, that is Sunday 29 November.
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