HP calcs with clock

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I wonder, which HP calculator models do have built-in RTCs?
AFAIK, these include HP-41, HP-71, HP-75, HP-48/49/50, 38/39/40, Prime.
And hi-end business models (which exactly?).

Also, I'm very confused with 28C/28S - all specs say it has no RTC, but there are lot of programs and docs using some king of internal timer. So, does 28 has any kind of internal clock/calendar ticking while calc is off? HP-42S?

tia
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