On Hacker News user bertil wrote interesting comment (bold mine):
The idea that a meeting is a date or not has to be clarified. You can’t just have a drink with a colleague, and let the romantic interest to-be-determined. Americans, as I understand it, tend to have “the talk” which is a clear idiom for an actual conversation where they mutually decide to “be exclusive”, i.e. not take dates with other people. Timing, number of dates and all that are also fairly established.
I have regularly seen in several countries in Europe a relationship going from inexistent to committed, public and exclusive in a matter of hours. “Having the talk” is often understood as an intent to break-up (because it sounds like “We need to talk”). Whether a meeting has a romantic interest is never really expressed: it’s generally either obvious or purposely vague than anything. That has lead many American friends in Europe very frustrated with the dating scene, because it comes off as unreadable. Europeans in the US can find the formalism icky, but they generally adapt more easily.
There are also far more differences between European countries (wolf-calls are apparently common in Italy; Scandinavia can come of as the opposite) than with the US — but formalism is certainly the big one.
What does means "wolf-calls" in the last sentence?
Is it some new idiom?
I've tried to google it, but had no luck.