BHASKARA I LAGHUBHASKAREEYA (628 AD)
Desaanthara ghatee kshunnah madhyaa bhukthir
dyuchaarinaam shashtyaa bhaktham runam praachyaam rekhaayaa:
The time is calculated based on the meridian. Divide the time by 60… and the longitude is calculated.
Towards the east subtract and towards the west add the number (Laghubhaskareeyam 1-31)