in classic NT4 domains "never expires" was a value of 32bit unix epoch max (2036-02-05), samba-tool domain classicupgrade should be aware of that and correctly set those account to "never expires", too.
This bug was referenced in samba master: df75d82c9de6977c466ee9f01886cb012a9c5fef
Karo, the commit should also be cherry-picked to the supported release branches.
(In reply to Björn Jacke from comment #2) Pushed to autobuild-v4-{14,13,12}-test.
This bug was referenced in samba v4-13-test: ac0e7f6a0cd6a27679762556324a6ec755401824
This bug was referenced in samba v4-14-test: dedae240651b50c44eefd3b4d15f35621085cdb4
This bug was referenced in samba v4-12-test: 237a51d926e1620dd185cd55c3d9dbfb443b44e8
This bug was referenced in samba v4-14-stable (Release samba-4.14.0rc3): dedae240651b50c44eefd3b4d15f35621085cdb4
This bug was referenced in samba v4-13-stable (Release samba-4.13.5): ac0e7f6a0cd6a27679762556324a6ec755401824
This bug was referenced in samba v4-12-stable (Release samba-4.12.12): 237a51d926e1620dd185cd55c3d9dbfb443b44e8