what keeps time between calls to time server?

Well, never mind. I found it:

unsigned long NTPClient::getEpochTime() {
  return this->_timeOffset + // User offset
         this->_currentEpoc + // Epoc returned by the NTP server
         ((millis() - this->_lastUpdate) / 1000); // Time since last update
}

In between getting the time from elsewhere, the local process just uses millis().

Missed that reading quickly time after time, so. I blame the formatting of the expression forming the retune value. Yeah, that's the ticket.

a7