Sometimes you'll know the age of a person, or at least the era or generation which influenced them, by looking at the words they are using.
Some examples I noticed:
"ASEAN" instead of "South-East Asia". You know they're young and grew up in the era when ASEAN is the focus.
"Southeast Asia" instead of "South-East Asia". The former is the preferred way today, the use of hyphens is disappearing. The latter comes from pre-21st Century rules.
Abbreviating "South" or "Southern" to "So" like "SoKor", "SoCal", "SoViet". Similarly, for "North" / "Northern" into "No", like "NoKor".
The use of "Occidental" and "Oriental" instead of "West" and "East" respectively. The former is the old way. The latter is what's common today.
"Xerox" instead of "photocopy".
"Photo" instead of "Picture". Picture now means the old way of developing your, well, pictures. Photo is now more understood as digital.
"Blog" or "Vlog" instead of "Journal" or "Diary". Who writes on paper these days, right? It's all digital now.
"Wikipedia" instead of "Library". Why visit a Library when you can search Wikipedia?
Of course, culture also plays a role, which also helps knowing whence a person grew up (or their family).
How about you? What words or phrases that gives you a signal about a person's origin and generation?
