In GnuPG I can edit the expiry of my key like this:
$ gpg --edit-key 01234567
[...]
gpg> expire
Changing expiration time for the primary key.
Please specify how long the key should be valid.
0 = key does not expire
<n> = key expires in n days
<n>w = key expires in n weeks
<n>m = key expires in n months
<n>y = key expires in n years
Key is valid for? (0)
But what if I want to set the expiry to a specific (absolute) date/time, e.g. 01-01-2015, midnight? Do I really have to calculate the exact time from now, e.g. 9m+15d+…?
Best Answer
The output of GnuPG on how to specify the expiry is missing the option to just enter an ISO date in the form of YYYY-MM-DD. Unlike the help text suggests it would not be valid, it will just work: