http://elpais.com/elpais/2014/02/23/...30_114153.html

Four centuries after Spain's literary giant Miguel de Cervantes Saavedra died in poverty, Madrid officials will soon embark on an exhaustive search for his grave.

The regional government has given the go-ahead for City Hall to hire a team of experts who will exhume the bones of an adult male buried inside the Trinitarias convent, in the capital's Las Letras neighborhood. The novelist was buried somewhere inside the convent on April 23, 1616.
(from wikipedia):
While 23 April 1616 was recorded as his date of death in some references, and the date on which his death was widely celebrated, he in fact died in Madrid the previous day, 22 April.[21] He was buried on 23 April.[22]

William Shakespeare died on 23 April 1616. To honor this, UNESCO established 23 April as the International Day of the Book.[23] However, these dates refer to different days: Spain had adopted the Gregorian calendar in 1582, but England was still using the Julian calendar. Shakespeare's death on 23 April 1616 (Julian) was equivalent to 3 May 1616 (Gregorian). This was 10 days after Cervantes was buried and 11 days after he died.