Put this in modules/contrib/ns_backdate.c.

ns_backdate.c

/*
 * Copyright 2014 Alyx Wolcott
 * Rights to this code are as documented in doc/LICENSE.
 *
 * Gives services the ability to backdate nicknames
 *
 */

#include "atheme.h"

DECLARE_MODULE_V1
(
	"contrib/ns_backdate", false, _modinit, _moddeinit,
	PACKAGE_STRING,
	"Atheme Development Group <http://www.atheme.org>"
);

static void ns_cmd_backdate(sourceinfo_t *si, int parc, char *parv[]);

command_t ns_backdate = { "BACKDATE", N_("Change registration date of an account."), PRIV_USER_ADMIN, 3, ns_cmd_backdate };

list_t *ns_cmdtree, *ns_helptree;

void _modinit(module_t *m)
{
	MODULE_USE_SYMBOL(ns_cmdtree, "nickserv/main", "ns_cmdtree");
	MODULE_USE_SYMBOL(ns_helptree, "nickserv/main", "ns_helptree");

	command_add(&ns_backdate, ns_cmdtree);
}

void _moddeinit()
{
	command_delete(&ns_backdate, ns_cmdtree);
}
static void ns_cmd_backdate(sourceinfo_t *si, int parc, char *parv[])
{
	myuser_t *mu;
    mynick_t *mn;
    char *target = parv[0];
    char *stime = parv[1];
    if (!stime)
        goto failure;
    time_t mytime = (time_t)strtol(stime, NULL, 10);
	/*char *target = parv[0];*/
	/*char *action = parv[1];*/
	/*char *reason = parv[2];*/
	user_t *u;
	mowgli_node_t *n, *tn;

	if (!target || !time)
	{
        goto failure;
	}

	mu = myuser_find_ext(target);

	if (!mu)
	{
		command_fail(si, fault_nosuch_target, _("\2%s\2 is not registered."), target);
		return;
	}

    mu->registered = mytime;
    MOWGLI_ITER_FOREACH(n, mu->nicks.head)
    {
        mn = (mynick_t *)n->data;
        mn->registered = mytime;
    }

    command_success_nodata(si, "Successfully changed time for %s", target);
    return;
	
failure:
    command_fail(si, fault_needmoreparams, STR_INSUFFICIENT_PARAMS, "BACKDATE");
	command_fail(si, fault_needmoreparams, _("Usage: backdate <account> <unix timestamp>"));
	return;

}

/* vim:cinoptions=>s,e0,n0,f0,{0,}0,^0,=s,ps,t0,c3,+s,(2s,us,)20,*30,gs,hs
 * vim:ts=8
 * vim:sw=8
 * vim:noexpandtab
 */