...
[root@server1 ~]# systemctl stop ntpd.service
3- change the date ( manually)
[root@server1 ~]# timedatectl set-time '2016-06-01 18:44:30'
[root@server1 ~]# date
Wed 1 Jun 18:44:32 BST 2016
[root@server1 ~]# timedatectl
Local time: Wed 2016-06-01 18:44:36 BST
Universal time: Wed 2016-06-01 17:44:36 UTC
RTC time: Wed 2016-06-01 17:44:37
Time zone: Europe/London (BST, +0100)
NTP enabled: no
NTP synchronized: no
RTC in local TZ: no
DST active: yes
Last DST change: DST began at
Sun 2016-03-27 00:59:59 GMT
Sun 2016-03-27 02:00:00 BST
Next DST change: DST ends (the clock jumps one hour backwards) at
Sun 2016-10-30 01:59:59 BST
Sun 2016-10-30 01:00:00 GMT
...
[root@server1 ~]# systemctl start ntpd.service
...
5- On the client: stop, resync, start and check the date/time again
[root@centos7 ~]# systemctl stop ntpd.service
...