Now.

Having had decades of this in geophysical exploration, the time is now AND (where relevant) it's the current UTC Zulu time AND it's both local times.

Any data collected is logged against a UTC sync for start of recording (and continues with lapsed time AND logging raw GPS times .. which sorts out leap second issues).

Any discussion re: start of next data collection is relative to the local time at the field end, the planes et al are often bound by daylight - so field operation local dawn and sunset are relevant.

Any discussion re: software changes | hardware support is relevant to the local time at the home office end as that'll rest on when the office staff or aircraft mechanics come in or free up.

For ease of communication many such discussions are along the lines of "we'll ring back in four hours and ...". That's a NOW relative epoch.