Sign

The twelve signs used In Tibetan astrology are: Mouse, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Sheep, Monkey, Rooster, Dog and Pig.
As there are 5 elements and 12 signs it is easy understandable that there are 60 combinations.
The elements are each used twice when the signs change.
E.g. Wood - Mouse, Wood - Ox, Fire - Tiger, Fire - Rabbit, etc.
Although the Tibetan cycle 1 start in the year 1027 the Chinese cycle 62 which starts in 1024 is used for the calculations.
But there exists also a connection with the nine mewas which start in 1024 with Green 4, followed by Blue 3, Black 2, White 1, etc. and so it takes three cycles ( lower, middle and upper cycle of 60 years) totalling 180 years for a full cycle to complete. So for the mewa's it is important to know which cycle is used.
The even years are male and the odd years are female.

Year:
The year sign and element can easily be calculated if you know a certain year and as we do know that the year 1024 is a Wood - Mouse year we start from here.
Let's calculate for the year 2012.
For the sign:
( 2012 - 1024 ) / 12 = 82 remainder is 4.
Using the remainder start at Mouse = 0, Ox = 1, Tiger = 2, Rabbit = 3, Dragon = 4 which is the Sign.
For the element:
( 2012 - 1024 ) / 10 = 98 remainder is 8.
Using the remainder start at Wood = 0, Wood = 1, Fire = 2, Fire = 3, Earth = 4, Earth = 5, Metal = 6, Metal = 7, Water = 8 which is the element.
Year 2012 Water male Dragon

Month:
Once you know the year you can find the month sign and element.
The month signs are always month 1 = Dragon, month 2 = Snake, month 3 = Horse, etc.
The month element depends on the element of the year.
The year starts at the 11th Tibetan month.
Let's calculate the fifth month of 2012:
The Sign is Monkey.
For the element the child of year element is taken which is Wood.
This one is used for month 11 and 12.
Fire the child of Wood is used for month 1 and 2.
Earth he child of Fire is used for month 3 and 4.
Metal the child of Earth is used for month 5.
The male monthes are: Mouse, Tiger, Dragon, Horse, Monkey and Dog.
The female monthes are: Ox, Rabbit, Snake, Sheep, Bird and Pig.
Year 2012 Water male Dragon, Month 5 Metal male Monkey

Day:
Once you know the month you can find the day sign and element.
Care has to be taken to use the correct day as sometimes days are omitted and sometimes days are doubled.
Let's calculate for day 6 of month 5. ( there are no missing or doubled days before day 12 ).
It is important to know the gender of the month to find the correct day sign as for the male month the first day sign starts with Tiger and the first day sign for female month starts with Monkey.
So as this is male month we start
Tiger = 1, Rabbit = 2, Dragon = 3, Snake = 4, Horse = 5 and Sheep = 6 which is the sign.
For the element we start with the child of the month element.
Water = 1, Wood = 2, Fire = 3, Earth = 4, Metal = 5 and Water = 6 which is the element.
Year 2012 Water male Dragon, Month 5 Metal male Monkey, Day 6 Water Sheep

Hour:
Once you know the day you can find the hour sign and element.
Important to know is that a Tibetan day start at 05:00 and that every two hours have assigned signs.
E.g.
05:00 - 06:59 Rabbit
07:00 - 08:59 Dragon
09:00 - 10:59 Snake
.... etc.
23:00 - 00:59 Mouse
01:00 - 02:59 Ox
03:00 - 04:59 Tiger
So:
25th june 2012 at 05:00 is Tibetan year 2012, month 5, day 6
25th june 2012 at 04:59 is Tibetan year 2012, month 5, day 5
Let's calculate for 07:00
Sign is Dragon
For the Element start with the child of the day element.
Wood = 05:00, Fire = 07:00 which is the hour element.
Year 2012 Water male Dragon, Month 5 Metal male Monkey, Day 6 Water Sheep, Hour 07:00 Fire Dragon