The Internet Archive hosts various editions of the Kalnirnay calendar, including its evolution since 1973.
While a direct "official" download for 1986 is rare, you can find the relevant dates and astronomical data through these alternative sources:
In Vedic astrology, precision is paramount. If a person was born in 1986, an astrologer needs the exact sunrise, Tithi , and Nakshatra of that specific date to create a Janampatri (birth chart). Using a modern calendar to calculate a 1986 event can lead to errors due to the shifting of Adhik Maas (leap months). The 1986 Kalnirnay serves as a primary source document.