# Conversion between Gregorian date and Kali day number

Most of the popular calendar systems are not suitable for doing easy
manipulation and arithmetic on date and time values. It has been
recognized by scholars that a day count from a fixed epoch is the most
convenient way to represent date and time. Astronomers use Julian Day
Number, devised by John Herschel (who
discovered the planet Uranus) in the 19th century. Many software
libraries, including Microsoft's MFC, store date as the number of
days since 1900 January 1 or some other date. Unix/Linux systems use
the number of seconds since 1970 January 1.
Such a system has many uses:

- We can add or subtract a fixed time to date/time by adding the
value directly.
- The difference between two dates/times can be found by finding
subtracting the first number from the second.
- Weekday can be found from a single MOD operation.

Indians had this system a long back, at least since the 9th century.
They represented the so-called *Kali day number* as the number of days elapsed
since the Gregorian date January 23, -3101 (February 18, 3102
B.C.E. in Julian Calendar), the start of *Kali yuga*. Ancient Indian astronomical work
use the *Kali day number* for representing dates and expressed astronomical
results as its functions. South Indian
mathematicians used to represent *Kali day number* using a language device called paralpperu.

You can convert a Gregorian date to Kali day number and back using the
utilities below.

## Gregorian date to Kali day

** Last modified: Fri Apr 21 14:51:59 PDT 2006 by Umesh
**

Maintained by: Umesh, Sindhu and Vishakh