Yealink SIP-T54S Administrator's Manual page 287

Parameters
Web User Interface:
Settings->Time & Date->Daylight Saving Time
Phone User Interface:
Menu->Basic->Time & Date->General->SNTP Settings->Daylight Saving
local_time.dst_time_type
Description:
Configures the Daylight Saving Time (DST) time type.
0-DST by Date
1-DST by Week
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->Fixed Type
Phone User Interface:
None
local_time.start_time
Description:
Configures the starting time of the Daylight Saving Time (DST).
Value formats are:
Month/Day/Hour (for DST by Date)

Month/Week of Month/Day of Week/Hour of Day (for DST by Week)

If "local_time.dst_time_type" is set to 0 (DST by Date), use the mapping:
Month: 1=January, 2=February,..., 12=December
Day: 1=the first day in a month,..., 31= the last day in a month
Hour: 0=0am, 1=1am,..., 23=11pm
Example:
local_time.start_time = 1/1/2
If "local_time.dst_time_type" is set to 1 (DST by Week), use the mapping:
Month: 1=January, 2=February,..., 12=December
Week of Month: 1=the first week in a month,..., 5=the last week in a month
Day of Week: 1=Monday, 2=Tuesday,..., 7=Sunday
Hour of Day: 0=0am, 1=1am,..., 23=11pm
Example:
Configuring Basic Features
Permitted Values
0 or 1
Time
Default
0
1/1/0
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