Clock timezone CET +1
Clock summer-time CEST recurring first SUN April 01:00 last SUN Oc 01:00 < offset> (default 60)
ntp source loopback0
ntp server <ntp ip addr>
show ntp status (see synchronize, this may take up to 30 minutes)

To use the correct timezone for logs and debugs, you need to add this cmds:

For debug: service timestamps debug datetime msec localtime show-timezone year
For logs: service timestamps log datetime msec localtime show-timezone year

Enable the CallManager Advanced service parameter in CUCM:
“Allow Peer to Preserve H.323 Calls”  

on the Gateway:
voice service voip
   call preserve
   no h225 timeout keepalive