It is the 400th year of the Guru Granth Sahib, the Sikh holy book. The daily times has an article about this book, which tells us about the Sikh Gurus and also why Sikhs have turbans.
It contains, besides the works of the Sikh Gurus, writings of several Hindu and Muslim sages and holy men. Altogether there are 3,384 hymns of which nearly 1,000 are attributed to non-Sikhs. Among the Muslim saints whose contribution to the Guru Granth Sahib stands out clearly is Shaikh Farid. This way Sikhism is an eclectic rather than an exclusive creed. This breadth of vision truly captures the essence of the spiritual and humanist traditions of South Asia.
The hymns included were originally composed in several languages including Punjabi, Hindi, Sanskrit and Persian but have been made accessible to the Punjabi readers in the Gurmukhi script in which the Guru Granth is written. Recently it has been rendered into the Persian or