There are at least two different Tibetan calendars. The Tsurluk calendar is the one formulated by the 3rd Karmapa Rangjung Dorje (1284-1339.) In more widespread use is the Phukluk calendar which dates from the 15th century.
Nitartha's explanation of the calendrical traditions.
Various printed calendars are available from Namse Bangdzo.
In every Tibetan month, certain days are considered right for certain practices, and on those days the effects of positive or negative actions are multiplied 100 times.
8th Day -- Medicine Buddha
15th Day -- Amitabha Buddha
30th Day -- Shakyamuni Buddha
Other Special Days of the Month
10th Day -- Guru Rinpoche Day
25th Day -- Dakini Day
29th Day -- Dharmapala Day
Four Major Buddhist Festivals
The festivals (Tib. Du.chen) relate to events in the legendary life of Buddha Shakyamuni (the historical Buddha.)
For example, Chotrul Düchen., which occurs during the first 15 days of the Tibetan Buddhist year, commemorates the 15 days on which, in order to increase the merit and aid the devotion of future disciples, the Buddha displayed a different miracle each day. At times such as that, the benefits of practice are greatly multiplied.
The anniversaries that are observed can depend upon the denomination and lineage to which one belongs.
Anniversaries which fall in doubled months are usually celebrated in the second month, although they may be celebrated in the first month if more convenient for the practitioner. [In published calendars, dates of anniversaries are normally indicated in the repeated month.]
Tibetan Year of the Female Wood Sheep 2142 begins 18->19 February 2015
Most residents of the various historical Tibetan regions will celebrate Losar on or about Feb. 18th-19th.
End of Wood Horse, Beginning of Wood Sheep 2142 Calendar at FPMT (Foundation for the Preservation of the Mahayana Tradition)
with notes about special days, including auspicious days for beginning various endeavours and days NOT for hanging flags.
anniversary: From the Tibetan Buddhist perspective, the anniversary of a lama's death is cause for celebration rather than that of their birth.
Sogyal Rinpoche wrote:
“However consummate our spiritual mastery may be, we are still limited by the body and its karma. But with the physical release of death comes the most marvellous opportunity to fulfil everything we have been striving for in our practice and our life.
Even in the case of a supreme master who has reached the highest realization, the ultimate release, called parinirvana, dawns only at death.
That is why in the Tibetan tradition we do not celebrate the birthdays of masters; we celebrate their death, their moment of final illumination.”
Nevertheless, the 17th Karmapa, on the occasion of the celebration at Rumtek Monastery of his 18th birthday in 2006, commented:
Generally, samsara--the cycle of birth, sickness, old age, and death--is a cause of suffering and is to be abandoned. There is nothing about it to celebrate and honor. However, if a person born in this world is helpful to all sentient beings and serves the teachings of the Buddha, then this kind of birth is not to be belittled and should be praised and honored.
KARMA KAGYU SPECIAL DAYS cycle calculated by Michael Erlewine follows here.
Karma Kagyu Anniversaries (Birth of 17th Karmapa was 8th day of 5th Tibetan month, but is celebrated "internationally" on June 26th.)
Tibetan Month Day Anniversary
First 08th new prayer flags
First 08th 6th Karmapa, Tongwa Donden
First 09th Long life 7-day practice
First 14th Milarepa
First 15th Marpa
First 15th 7th Karmapa, Chodrak Gyatso
First 21st 14th Karmapa, Thegchog Dorje
First 24th 13th Karmapa, Dudul Dorje
First 28th 9th Karmapa, Wangchuk Dorje
Second 25th 8th Situ, Chokyi Jungne
Third 3rd 2nd Karmapa, Karma Pakshi
Third 16th Terton Mingjur Dorje
Fourth 01st Vajrakila rites, 11 days
Fourth 29th Mipham
Fifth 01st Chakrasamvara, 7 days
Sixth 05th Chod, 5 days
Sixth 14th 3rd Karmapa, Rangjung Dorje
Sixth 15th Gampopa
Sixth 15th Varsha (yarney) rain retreat, 45 days
Seventh 04th 13th Karmapa, Dudul Dorje
Seventh 15th 4th Karmapa, Rolpei Dorje
Seventh 21st Red Chenrezig mandala, 7 days
Eighth 01st 5th Karmapa, Deshin Sharpa
Eighth 23rd 8th Karmapa, Mikyo Dorje
Ninth 01st Terton Karma Lingpa, 5 days
Ninth 04th 2nd Karmapa, Karma Pakshi
Ninth 09th 16th Karmapa Rigpe Dorje
Tenth 03rd Vairochana, 7 days
Tenth 30th 12th Karmapa, Chanchup Dorje
Eleventh 03rd 1st Karmapa, Dusum Khyenpa
Eleventh 15th 10th Karmapa, Choying Dorje
Eleventh 22nd Wrathful Dorje Trolo, 9 days
Eleventh 22nd Dorje Bernakchen, 9 day
Eleventh 26th Jamgon Kongtrul the Great