Don’t they have Google where you come from?
JD =367K - <(7(K+<(M+9)/12>))/4> + <(275M)/9> + I + 1721013.5 + UT/24
- 0.5sign(100K+M-190002.5) + 0.5
where K is the year (1801 <= K <= 2099), M is the month (1 <= M <= 12), I is the day of the month (1 <= I <= 31), and UT is the universal time in hours ("<=" means “less than or equal to”). The last two terms in the formula add up to zero for all dates after 1900 February 28, so these two terms can be omitted for subsequent dates. This formula makes use of the sign and truncation functions described below:
The sign function serves to extract the algebraic sign from a number.
Examples: sign(247) = 1; sign(-6.28) = -1.
The truncation function < > extracts the integral part of a number.
Examples: <17.835> = 17; <-3.14> = -3.
The formula given above was taken from the 1990 edition of the U.S. Naval Observatory’s Almanac for Computers (discontinued).