FWIW, you can put the new card in the KLN-94 before the effective date.
The old data will be used until the
effective date. If you are using it at 0000 UTC on the effective date
(6pm CST) it will give you a message,
telling you to power off and back on to use the new data.

Which, IMO, stinks.

I was flying a night, IFR flight over Washington, DC, airspace, being
guided by GPS and the autopilot. Before you point it out: Yes, I got
caught with my pants down. I didn't have a current VOR tuned as a backup.


Well, in the case I was referring to, my KLN04 did not force me to
reboot at that moment, it just was letting me know that I would need to
reboot eventually to use the new cycle's data. It continued tracking
and using the old data just fine in the mean time.

Did yours actually force you to reboot at that moment? What kind of
GPS is it?

Cheers,
John