Dictionaries built with dictfmt / dictzip (often called .dict.dz) contain timestamps:

This file was converted from the original database on:

dictzip gzip-compresses the dictionary and includes a timestamp in the header.

Solution

Call dictfmt with --without-time to prevent the timestamp in the dictionary. See 776430.

In the case of dictzip a patch is needed, maybe the flag --no-name (-n).