Memorizing a 128 bit / 256 bit hex key

You thoughts please, gentlemen.

Let's say you travel and do not want to store your secret hex key on your
device and recreate it from memory.

What do you think about this proposal?

$ printf '%x' $(date -u -d '1979-01-01 12:34:56' +%s) $(date ...) 4 or 8 times.

One has to remember only the dates (times are optional) and then simply run the
one liner.

The encryption software can be downloaded when one arrives at his destination.

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Regards
Stefan