The relevant columns of my logbook (an oldish Airtour commercial logbook) are headed
Departure G.M.T (UTC)
Arrival G.M.T (UTC)
A Pooleys PPL logbook I take around with me before copying up later has columns headed...
t/o (GMT)
land (GMT)
And although I don't have it to hand, I'm pretty sure my old RAF issue logbooks from my mis-spent (comparative) youth say something similar also.
So I have always used Zulu. The only thing I ever complete in local time is airfield sheets which are often in local.
What I've never been quite sure of when significant distances from the UK, is whether the DATE is local or as at Greenwich?
G