Thanks everyone for all the admiration
Must take an up-to-date pic, she really is a stunner
Hillie has now produced hers, a half-brother-cum-uncle to Cherry. He's the same colour but has black-rimmed eyes and a black nose. Unlike Cherry he's not very active, in fact I nearly called him Dopey. (But decided on George - Dad is Atlas, lol. Hope he grows into that heritage!)
Plenty cooked Cherry for a whopping 293 days, trish.farm. She needed a bit of help - by hand - to push her out and you wouldn't have believed she was a newborn the following day, she already looked 5 days old, let alone she's half Jersey
Hillie is much more sensible, she popped George out with no fuss at all, at 286 days. A much smaller calf at birth, much more like a newborn!
The shortest gestation I've had with my Jerseys has been Hillie's last year's calf, a British Blue, which was about 282 days I think. I always calculate on 279 days (for the whole herd, this is, mainly Angus X and Hereford X) and have never had one early on that. Some bulls and some breeds are much longer, I would think our average is probably about 285 days. Some of the British Blues have been 279 and 280 days - they are supposed to be shorter gestation and therefore easier calving and that has been our experience.
I can't predict how your Jersey would do, but if it wouldn't be too difficult to fetch her up quickly if she started altering then end of the month sounds fine. If it's not easy to fetch her up when she starts altering then maybe you shouldn't risk it! My Jerseys start bagging up a good 10 days, often more, before they calve, their ligaments slacken over a period of days before calving, and their bags get really full and 'springing' when calving is imminent, so I'd have plenty of notice to fetch them in. But I don't know if that's all Jerseys or just mine.