Conferences: ill-formatted CNUMs

[jacquerie]

The following records have an ill-formatted CNUM:

• 1590071
• 1477158
• 1194030
• 980162
• 978008

The following record instead had an ill-formatted CNUM, which I fixed, but then I realized that maybe I shouldn't have, and decided to open this issue instead:

978083

CC: @annetteholtkamp @michamos

[michamos]

@ksachs Can you have a look at 1590071 that you added recently? I am not sure whether the starting date is correct.

[ksachs]

nothing wrong with the starting date. no idea where the wrong CNUM came from.

[michamos]

Thanks!