When building glibc localedata, gzip is used with -9 option, so timestamp of 
each compressed file is include.

First the timestamp/filename is not required.

Secondly, with timestamp removed, each charmaps gz file and locale-archive have 
always the same md5.
This make paranoid people looking why files are different happier.

Third, with timestamp removed, charmaps files are a few bytes smaller.

Even the oldest gzip I find (gzip-1.2.4) support the -n option.
So use gzip -9n
Index: localedata/Makefile
===================================================================
RCS file: /cvs/glibc/libc/localedata/Makefile,v
retrieving revision 1.109
diff -u -r1.109 Makefile
--- localedata/Makefile	31 Oct 2008 15:12:03 -0000	1.109
+++ localedata/Makefile	13 Dec 2008 19:42:41 -0000
@@ -114,7 +114,7 @@
 	$(make-target-directory)
 	rm -f $(@:.gz=) $@
 	$(INSTALL_DATA) $< $(@:.gz=)
-	gzip -9 $(@:.gz=)
+	gzip -9n $(@:.gz=)
 
 # Install the locale source files in the appropriate directory.
 $(inst_i18ndir)/locales/%: locales/% $(+force); $(do-install)