Where the numbers come from
We use research from university extension offices, the USDA and vet schools. We read the source ourselves and keep its exact words with each number.
We do not take numbers from other calculator sites, blogs or forums.
When two good sources do not agree, we tell you and show both.
Due dates
A due date is the breeding date plus the average number of days the animal carries its young.
Most animals give birth a few days before or after that date. So we also show the normal range from the research, and what share of births fall in it.
Breed matters. Where research gives a number for a breed, you can pick that breed.
The math
We count whole days on the calendar. Leap years are counted.
Each page shows its math, so you can check it by hand. Our tests check the math each time we change a page.
What we leave out
We do not give medicine or dewormer doses. Many are not approved for every animal, and only a vet can set them.
Sources and dates
Each page lists its sources at the bottom, with a link and a date.
Each page also shows when we last checked it. When a source changes, we change the page.