I've caught a breeding pair of cattle around 3AM CET on 15th of this month. I put them in the same pen and they were together for two RL days. Cow pregnancy takes 2 in-game weeks, or 4 days, 16 hours IRL. It's 3PM on the 22nd now, and still no calf (can't milk the cow, so no chance it has spawned outside and wandered off). We didn't have over two and a half days of downtime, did we?
Anyway, I suspected the pen might have been too small for sex (2x3), so I moved them to a bigger pen. Observed them for an hour, no sex. I'm suspecting that the cow is actually pregnant but not giving birth for some reason. Could a dev check if that's the case? The cow in question is Zelenka, on my farm (my hearth is there too).