I present UTC times in my browser GUI, but a friend that passed by last weekend told me he didn't know UTC and much preferred GMT tagged timezones.

It never occurred to me to fuss about this before.

How many people here are familiar with the UTC timezone format?

While he didn't mention anything about it, it also left me wondering whether people are familiar with the 24 hours clock (0:00-23:59) as well as the 12 clock (12:00 am - 11:59pm). I personally prefer the 24 hours clock (from engineering perspective, it's less conversion), but I'm unsure how widespread it is internationally.

As this is an international forum, I thought this might be a good place to inquire.

I can easily use both GMT and UTC (not that hard really :D ) and 12 / 24 hours clock. As for my nation, well, most Czech people don't know what GMT or UTC is and are clueless when asked which timezone are they in, but we do use military time.

We use the 24-hour clock almost exclusively. People will talk about something happening at three or five o'clock, but you'd never see that written anywhere, as it would be considered confusing. As far as I know, most of Europe is like that.

EDIT: Also, Czechs like ninjaing each other very much.

I'm familiar with UTC & the timezone format, though usually I write GMT+/- rather than UTC+/-, as more people seem to understand what that means.
Also, here the 24h system is the norm when writing time, though in everyday speech people still use the 12h system (and usually not defining when, we don't have the shorthands am/pm, so it is a bit more cumbersome to specify if it is am or pm, so people just use the context of the situation to explain if it is before or after-noon that they are referring to)

Thanks for the feedback.

It has been most informative.

Shame I could only give the answer to one person.