Bantracker duration parsing doesn't handle large values well

[stwalkerster]

<eir> Please comment on the following: ban[127515] nick!user@host was set on #channel by stwalkerster!~stwalkers@wikimedia/stwalkerster on 2019-10-15 09:52:35Z and had an expiry date of 2019-10-16 09:52:35Z.
<stwalkerster> ~999999999d my reason for "essentially forever" ban here.
-eir- I have suffered a terrible failure. (Perl call raised error: Died at (eval 5) line 816.

Granted, that number of nines is excessive, but a nicer error message would be appreciated, as well as morphing an expiry that long into something that is as good as effectively forever. (say, 100 years?)

Removing only two nines has given me a ban with an expiry date of 29398-11-08 09:53:44Z.