Document the time format of rndc dnssec -checkds -when <time>

Description

Setting the actual time of DS publication or withdrawal using

rndc dnssec -checkds -when <time> published <domain>

is documented only with this sentence in the rndc(8) manual page:

The time that the DS has been published  or
withdrawn is set to now, unless otherwise specified with the ar‐
gument -when time.

But the actual time format accepted is apparently not documented anywhere. I tried to use the same format rndc prints when the -checkds command is executed without -when parameter, but it did not work either:

$ rndc dnssec -checkds published my.dom.ain
Marked DS as published since 13-May-2022 10:44:05.000

$ rndc dnssec -checkds -when '13-May-2022 10:44:05.000' published my.dom.ain
rndc: 'dnssec' failed: syntax error

I tried several other time formats, but was not able to figure out which time format is accepted by the -when switch. Also, the "syntax error" message is not very helpful there.

This is rndc from BIND 9.16.27.

Request

Please document the time format(s) accepted by the -when switch, and maybe improve the diagnostics message printed when some of the switches have invalid arguments.

Thanks!