I can't read the clock in my radio during the day so I stuck an LCD
clock to my dashboard. Problem was I could not
read it as night without pressing a button to light the display.
Besides, it lost about a minute a week.

I thought I found the solution in the JC Whitney LED DIGITAL QUARTZ
CLOCK SKU#ZX812798R $15.95. I cut a hole in
my dash and installed it only to find two problems:
1. I could not read it during the day - The LED display was very dim.
2. It gained about a minute a week.

This digital was the only one I could find after an extensive search
so I resolved to fix these problems.

I ordered another clock to experiment with and took it apart. The
first problem resulted from a 0.80 thick plastic
lens in front of the actual LED. It was red and dimmed the light from
the LED behind it. I cut a slot the actual
size of the led in a piece of black plastic the same thickness - a
clear piece could be used but the the PC board
the LED is mounted on would be visible. I assume this is why they used
the red color on the lens.

The second problem was a little harder to figure out - I looked up the
quartz crystal (3.93216 MHz ) which the clock
depends on for accuracy.
There is a pair of capacitors used to load the crystal and the
required value was specified at 17 pico-farad.

I found useful information on crystal timing at:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/555
The first thing was that a clock running fast can be adjusted by
increasing the capactor values. The second thing
was a formula the total value for capacitors hooked up in series. If
they are the same value, the total value
is half the value of the individual capacitors.

I found the load capacitors in the clock were 15 pf which calculates
out to a load value of 7.5pf versus the 17pf
specified. I substituted two 33pf ceramic capacitors for a calculated
value of 16.5pf - much closer to the 17pf
specified. The result was the clocks (I changed both) now gain or
loose 1 second or less in a week of testing.

You may wonder why I went to this much trouble -
1. I could not find another clock that might work.
2. I had cut a hole in my dash which the clock fitted into.