depicting daylight saving time
vertical decliner, calendar and Italian lines,
and summer time (daylight saving time)
To the right is a vertical decliner dial, it has winter time on
the winter solstice, or upper, curve, and summer time on the
summer solstice, or lower, curve. It is that easy.

The formula is simple, summer time is usually 1 hour later
than winter time. So, on the noon line there would be winter
time as 12 noon, and summer time would then be 1pm, and
so on.
See also: summer time, daylight saving
Illustrating Time's Shadow ~ page 32 in chapter 5
Rohr ~ page 30 Sundials History, Theory, and Practice
Waugh ~ page 17, Sundials Their Theory and Construction
Mayall ~ page 94, Sundials, Their Construction and Use
Cousins ~ page 79, Sundials, The Art and Science of Gnomonics
Another dial with winter time on top,
summer time on the bottom. It also
has Italian lines.
a short humorous video on daylight saving time