In the "Preferences" dialog, "Places" tab the default place details also contain the current timezone for that location. If you don’t want to have to remember to adjust that timezone for daylight savings yourself, then you can switch on this option, so that every time that Solar Fire starts up, it will check the current timezone according to the Atlas timezone tables, and set it accordingly for the current date.
However, if for any reason the place you have selected as your current default place is not linked to a timezone table, then using this option might result in a warning message each time that Solar Fire starts up, and the timezone will not be updated. In this case you have the option of either switching this option off, or of re-selecting your current location.