The next complicating factor is that there are really less than 360 days in a true lunar year, so certain days must be omitted. As a result, there are squares on the Tibetan calendar (which resembles a chessboard) with no number, only the word chad (which means "cut off"). That day of the month simply does not exist during that particular year.

Sometimes a day is considered inauspicious and, in order to avoid it, that date is also omitted and similarly does not exist in that particular year. Instead, the same date (that is, the previous day's date) will appear in two consecutive squares.

Tibetan months are numbered, rather than named, but days of the week and years are named. Similar to the West, weekdays are named after the sun, the moon, and five of the visible planets.

Prior to the 11th century the calendar was based on a 12-year cycle and each year was named for an animal: mouse, ox, tiger, hare, dragon, serpent, horse, sheep, ape, bird, dog and hog.

In the 11th century, a 60-year cycle was developed by adding the names of the five elements (wood, fire, earth, iron and water) to the names of the animals. The same element is combined with an animal for two years in succession. To eliminate confusion between two successive element years, "male" is added to the first year and "female" to the second. Thus, the Wood-Male-Mouse year is followed by the Wood-Female-Ox year. This 60-year cycle, begun in 1027 AD, is called Rabjung and a single year is called Lokhar. The Tibetan New Year begins with the rising of the new moon in February or March, depending on when the extra month has been added. Traditionally, towards the end of each year a new calendar was worked out by Tibet's State Astrologer and no one knew the next year's dates until that year was almost upon them.