I’m pushing 40, have a mind like a steel trap for phrases and terms that crop up in pop culture, and have a business degree. I have never heard “H1” or “H2” before, let alone “1H”. To me that suggests that it’s not a common term in British or American English and instead is common in another language. Kind of like Swedes and numbering the weeks of the year (perhaps the other Scandinavian countries do it too), or the various languages that interpret “half one” as meaning halfway to one (i.e. 1230) rather than half past (1330).

Of course it could just be a bizarre blindspot and it’s passed me by but damnit, I’m curious now!