Look at the sundial time indicated by the shadow. The shadow will be cast on markings for the time of day. Make a note of this number.
Adjust for the location within your time zone. Add four minutes to the sundial reading for every degree you live west of the center of your time zone. For every degree you live east of it, subtract four minutes.
Adjust for daylight-saving time. If daylight-saving time is in force, add one hour to the sundial reading.