When a new watershed is created, you must select the appropriate time zone representative of the watershed. This typically would be the time zone for the outlet or major portion of the watershed. Internally, CWMS will store time series data using the fixed "standard time offset from GMT" for the selected watershed time zone. Thus, the data will be held in standard time only. However, when viewing data or model results, you may select local or any other time zone for display purposes (which provides standard and daylight time labels, as appropriate, throughout the year).
You cannot change the watershed time zone once a watershed has been created. However, at any time you can customize the display of data from the View menu.