DST observance is based upon the Timezone you choose in the Date/Time Group. If your area doesn't observe DST then you should choose another timezone. An example of this within the United States is Arizona who has a separate GMT -7 entry in the list than the rest of Mountain Standard Time options since they don't observe DST.
now i want to disable DST ( if it is applicable ) or i want to set a new date/time group but how can i scape from this issue of DST with the new Group
Either change the existing DTG or create a new one, assign it to the phones' device pool and then reset them. They will pick up the change.
i also want to ask if i setup new NTP server with the new group is this can by any way affect our database (as this is a production enviroment)
The NTP references shown on the DTG are only applicable to SIP phones and has no impact on CUCM itself. SCCP phones always obtain their time through the registration process. Without an NTP reference the SIP phones obtain their time reference through their SIP REGISTER process to CUCM. The NTP server reference on CUCM is quite critical so use caution when modifying what the CUCM Publisher is synced to.
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