It's actually quite embarrassing how often you slip into 24 hour when talking to people that don't use it; fortunately for me most of my friends understand (both the system and my habits) but it's worse when you add "Z" or say "local" after every time.
We do this because some of our clocks are kept on GMT time (called "Zulu" time or "Z" - pronounced "Zed") and some are on local time (BST for example) called "local." Some of our clocks, in fact pretty much all of them, have the letter Z or L written on the clock face so you know what zone it's set on.
To further confuse things some time zones have their own designation so you might have a clock on Z, one on L and one on P time; it's weird hearing "aircraft due in a eleven thirty papa."
Further to the original question, for single digit hours people either use "oh" or "zero" depending on personal preference and it's not guaranteed to remain consistent. I know I usually refer to the shift start time as "oh-seven-fifteen" but I might call 5 am "oh-five-hundred" or "zero-five-hundred."
And 32 is definitely NOT old! 82 I'll start to accept as old but only just. (Yeah, that's the number of candles for me as well and I haven't even had a sub-life crisis yet, let alone a mid-life one!)