Conversation so far:
Who is Guru Arjan?
Guru Arjan was the first of the two Gurus martyred in the Sikh faith and the fifth of the ten total Sikh Gurus.
What is interesting about the Guru Arjan article?
He compiled the first official edition of the Sikh scripture called the Adi Granth, which later expanded into the Guru Granth Sahib.
Did Guru Arjan have any other major accomplishments besides the Adi Granth?
Guru Arjan compiled the hymns of previous Gurus and of other saints into Adi Granth, the first edition of the Sikh scripture, and installed it in the Harimandir Sahib.

Question: What years was he active?
Self-contained rewrite: What years was Guru Arjan active as fifth Guru?