This is the prime time to keep your distance - a very young calf a few days ago, the first of the season.
With my dog (who is terrified of them and is therefore always on a lead) I walk in, among and around this herd regularly. Once the calves are a few weeks old their mothers seem to calm down but at this stage they can be very protective. And there are extreme cases even among generally placid Highlands. A few years back the farmer warned me that one of the cows had taken off into the forest to give birth and that she was very aggressive in protecting the little one - they couldn't get near to tag the calf. "Watch out for number 72" he said. A few days later me and the dog rounded a corner on a forest track well away from where she had last been seen and who should step out of the forest in front of us but number 72. She fixed us with a basilisk stare and began to stride purposefully towards us. It's an open question as whether the whippet or me turned and ran the faster. She followed us just long enough to ensure that we were gone then returned to her calf. She could, of course, have caught up with me easily, but I knew, even if the dog didn't, that she wouldn't stray too far from the calf in its nest in the forest. Number 72, I might add, is no more. They decided that she was too dangerous.
All that said, other than with very small calves, I find the Highlands very tolerant, much more so than other breeds. The bull that used to be with this herd was even more so. He was generally keen to have me scratch his head. though I'm not recommending that as a technique of pacification. Best advice is give them a wide berth...