To set Date, Timezone, and Time in CLI:
(config)#system date <year> <month> <date>
(config)#system time <hour> <minute> <second>
(config)#system timezone continent/country/region
  Example: (config)#system timezone "North America/United States/Pacific Time"

To set Date, Timezone, and Time in WebUI, ArrayOS 6.4 or later :
Set Date and Time: under General Settings -> Date/Time tab
Set Timezone: "uncheck GMT" (if it is checked), now set your continent, country, and Timezone