There is a period of the day when the damaging rays (ultraviolet) of
sunlight is less or the least harmful to the body/skin. This was the
results of a study done some time ago. What period(s) of the day is
this? Hope you can help.

I'm not a researcher, and this isn't a direct answer to your question,
but I would like to make a comment.  The times I've gotten the most
sunburn are cloudy days and cool days, because when I don't feel the
hot sun on my skin, I forget to take precautions.  So in a warped
sense, these are the days when the sunlight is most harmful to *my*
skin.

The time of the day when UV is at its weakest is, well, midnight. 
Sorry to sound like a smartass, but it's true.

The strength of UV goes largely based on the sine of the angle between
the sun and the horizon.  The answer you're probably looking for,
therefore, is that at sunrise/sunset (when this angle is near zero),
UV is at its weakest.  This assumes you are on land, because if you
are on a large body of water, say a lake or ocean, it reflects UV
towards you, making you get a higher dose of UV.

The times during the day when UV rays are most damaging are between
approximately 10 AM and 3 PM.  This is due to the sun being (almost)
directly overhead during this period.  This link is so great, in fact,
that at high noon, the UV exposure is nearly 10 times that of 3 hours
before or 3 hours after high noon.

I say high noon instead of 12:00 because depending on time zones, your
location, and whether its DST or PST or whatever, 12:00 noon does not
necessarily equal high noon.

With regards to graememcrae's comment, on a cloudy/cool day, many
people feel it is unnecessary to apply sunblock, even though it's the
UV that is burning us, not the IR (heat we feel).  Unfortunately, UV
goes through clouds like, water through a sieve, and people get burnt.

Remember - always wear sunblock, and always wear UV protective sunglasses.

This link gives some useful info about sun-safety.

http://www.mormonchic.com/healthy/sun_safety.asp

You don't want to forget about air pollution.  If you live in a big
city, you are exposed to less UV as the day progresses.  I don't know
to what degree, but pollution protects us from sunburns.

Here's a site explaining the UV index:
http://www.ehso.com/ehshome/uvIndexInfo.htm

Accronding to me, the sunlight is less or the least harmful to the body
durning the evenings. also Ayurveda says that "Pokkuveyil"
(the evening sum's rays) makes ur skin glow like gold.

Here is a link to explain why you should NOT use sunscreen.
http://www.mercola.com/2004/may/26/summer_sun.htm

Sunscreen blocks the low intensity UV light but does not block the
high intensity UVA which goes deeper and effects your DNA. By using
sunscreen you are blocking your tan and spending more time exposed to
UVA. A good tan is the best block for UVA.

"Scientists are unsure whether sunscreen prevents against melanoma,
the deadliest type of skin cancer that accounts for more than 75
percent of skin cancer deaths. They suggest that sunscreen may prevent
sunburn, but may fail to protect against cancer. Sunscreens are
designed to absorb energy from ultraviolet light, however the energy
may be transferred to the DNA in skin cells, which could cause
problems.

Some studies have even found a link between melanoma and sunscreen
use, though researchers suggest this may only show that people who are
easily sunburned, who are more likely to get melanoma, are also more
likely to use sunscreen.

Researchers still recommend using sunscreen as it does protect against
basal cell carcinoma, the most common skin cancer that is usually easy
to treat, and sunburn, and it slows the wrinkling of aging skin."

The Baltimore Sun July 14, 2003

You have got to be kidding me...don't use sunscreen?  That's probably
the stupidest thing I have ever heard.

The doctor does raise some important issues like how sunlight is
required to produce Vitamin D, and of course, we need vitamin D to
absorb calcium, and so on and so forth, but sunscreen does not
completely block all rays.  And YES, it DOES block harmful UVA and UVB
rays.  Look at the label.  It clearly states it does right there.

As far as sunscreen being "regulated by the FDA because it contains
active ingredients", so does toothpaste.  So does anti-bacterial soap.
 Let's stop using those too, while we're at it...

My advice -- and that of pretty much any self-respecting doctor out
there...if you're going to be in the sun for a while, use some
sunscreen.  If you don't, you're going to look like those old people
at the beach who are all wrinkly and freckly.  Your call.

Looking at Atonewith's link, I cannot believe that that guy claims to
be a doctor!! ! Each molecule has a certain wavelength of light which
it absorbs, and DNA absorbs at 260 nm, which is-- you guessed it-- UV
light. When DNA absorbs that wavelength, it causes thymidine (one of
the four types of nucleotides in DNA-- the "T" in "A,T,G,C") to pair
together in what are called thymidine dimers. This messes up how the
DNA is read and pairs with itself and transcription enzymes. The body
has repair enzymes to fix the problem, but with too much exposure, the
DNA will be permanently messed up and cause the cell to overgrow
(i.e., CANCER!). What a fool.