Different Julian dates in SQLite and GLib, which is correct?

Question

I get different Julian dates for the same Gregorian date depending on the API. For the Gregorian date 2025-02-05:

• According to longpela, the Julian date is 25036.
• According to GLib, the Julian date is 739287.
• According to SQLite, the Julian date is 2460711.5.

Which is correct?

GLib:

#include <glib-2.0/glib.h>
/* gcc main.c -I/usr/include `pkg-config --cflags glib-2.0` `pkg-config --libs glib-2.0`  */

int main(int argc, char *argv[]) {

    GDate *dmy = g_date_new_dmy(5,2,2025);
    guint32 my_julian = g_date_get_julian(dmy);
    GDateDay day = g_date_get_day(dmy);
    GDateMonth month = g_date_get_month(dmy);
    GDateYear year = g_date_get_year(dmy);
    g_print("YYYY-MM-DD = %02u-%02u-%02u\n",year, month, day);
    g_print("Julian = %u\n", my_julian);

    return 0;
}

Output:

YYYY-MM-DD = 2025-02-05
Julian = 739287

SQLite:

/* From an SQLite session */
SELECT julianday('2025-02-05');
2460711.5

Answer 1

A Julian representation is simply a count of days since some fixed day in the past (the epoch).

GLib.Date doesn't return true Julian date as it doesn't use the standard Julian period epoch value, i.e. "Jan 1, 4713 BC". Instead, GLib.Date uses "Jan 1, 1 AD" as epoch. ^{[1] [2]}

The return value from sqlite3 is in line with this US Navy site, both use "Jan 1, 4713 BC" as the epoch for the current Julian period.