Checking for zone expiration?

[Alan Batie]

We had a rather key zone mysteriously expire on a slave this morning -
the log files show a transfer a couple weeks ago, but it hadn't been
updated so there was no reason for one since and there were no log
entries about failed connection attempts.  I was wondering if there's a
way to check the remaining time on a zone for monitoring?  If you fetch
the SOA, you get the full ttl, for obvious reasons, not the server's
timer...