Yealink SIP-T2 SERIES Administrator's Manual page 214

Administrator's Guide for SIP-T2 Series/T19(P) E2/T4 Series/CP860 IP Phones
Parameters
local_time.offset_time
Description:
Configures the offset time (in minutes) of DST.
Note: It works only if the value of the parameter ―local_time.summer_time‖ is set to 1
(Enabled).
Web User Interface:
Settings->Time & Date->Offset(minutes)
Phone User Interface:
None
To configure the DST via web user interface:
1. Click on Settings->Time & Date.
2. Select Disabled from the pull-down list of Manual Time.
3. Select the desired time zone from the pull-down list of Time Zone.
4. Enter the domain name or IP address in the Primary Server and Secondary Server
field respectively.
5. Enter the desired time interval in the Synchronism (15~86400s) field.
6. Mark the Enabled radio box in the Daylight Saving Time field.
Mark the DST by Date radio box in the Fixed Type field.
-
Enter the start time in the Start Date field.
Enter the end time in the End Date field.
192
Permitted Values
Integer from -300 to 300
Default
Blank