If you have set the timezone correctly ("print - $TZ") it changes atuomatically.

There are several timezones with their daylight savings already predefined, but you can use your own if nothing suits you. The command to change the timezone setting is "chtz", but you can use a SMIT panel for that: "System environments"/"Change / Show Date and Time" ("smitty chtz_date").

For instance have a server in Germany, where the DST starts on the last Sunday of March and ends at the last Sunday of October. The TZ variable reads:

NFT-1DFT-2:00:00,M3.5.0/02:00:00,M10.5.0/03:00:00

That means:

NFT-1DFT is the timezones name, "Norway (to) France, -1h DFT"

M3.5.0/02:00:00 The DST starts on the "5th" Sunday of month 3, that is the respective last sunday in the month March at 2 am

M10.5.0/03:00:00 The DST ends on the "5th" Sunday of Month 10, the last Sunday of October, at 3 am.

DST is achieved by adding one 1 h at 2 am onthe last Sunday in March, so the clock will go from 2:00 to 3:01 and having the clock stand still on the last Sunday in October, so at 2:00 am the clock is stopped and starts working one hour later.