MOON PHASE CALCULATOR
This is the only gadget you'll ever need for finding the moon phase on a given date. In seconds it will tell you the phase for any date until the year 4000 or for the last 2000 years. So if you need to carry out ritual or cast a spell at a specific phase of the moon, you can plan it as far in advance as you like. As it happens, you can also find the Moon Rise and Set times and also how long the Moon should be visible on a given day.
It looks very complicated (it does carry out some very complex calculations), but honestly, it really is very simple to use (the instructions are even printed on the back for reference so you never have to remember anything).
Guided Tour
Here's a quick guided tour so you can judge for yourself:
The calculator comprises 3 rotatable disks, one on top of the other, and each marked with a scale. The outer 2 (Yellow) scales are used to select the year (2006 in our example below) and the Inner (White) scales are used to select the month and view the phase of the moon - that's all there is to it. With 5 minutes practice you'll be a master. OK, we'll go through a quick example; Suppose we want to find the phase of the moon on 14th January 2006. We just follow the simple 4 step process shown in the diagram below and we can see in seconds exactly, what we want to know: 
The Process Explained
Step 1 - We search the outer scale to find the first 2 digits of the year (20) in our example.
Step 2 - Now we find the second 2 digits of the year on the next inner scale and rotate the two disks so all the numbers of our selected year are in alignment. OK, so that is the year selected (2006 for our example). We've purposely picked the hardest possible example to show you even that is easy. Now we just need to mentally make a note of the colour of the last 2 digits of our year (on the scale, some numbers are marked in Red and some are Blue - in our case we're using 06 which is Red but if we'd chosen 44, for example, they would have been blue).
Step 3 - On the inner (White) scale find the little black arrow pointer and turn the inner disk so the black arrow points to the month of interest. But, wait a minute, JAN and FEB seem to have 2 possible positions, so which do we set the pointer to? - Its easy, you'll see that JAN and FEB have marker lines with a red and a blue arrow pointing to them. If the colour in Step 2 was Red (as in our case here) then we select the line marked with the red arrow, otherwise we use the blue. This is done to take account of February which can have 28 or 29 days. All of the other months have only a single line so its even easier.
Hopefully the diagram below will clarify this for you:
Step 4 - Finally, now that the calculator has been correctly set for your target year and month, you can see at a glance, the exact Moon Phase for any day in that month - See the diagram above for our example which shows on the 14th Jan 2006, the Moon was Full. Like we said, before, it really isn't hard to master this device and it is a very useful tool. You'll never need to search the Internet or carry a special diary to find the moon phase, you can now see it for yourself for any date you like. Make no mistake though, this is a precision tool which carries out very complex calculations. In fact it is very similar to the sort of calculators used by aircraft pilots for solving navigation problems. It is a sturdy little device and should give many years of service.
Buy a Moon Phase Calculator