Function toJulianDate

toJulianDate(date: CalendarDateTime): number
Convert a calendar date/time to Julian Date

Uses the Meeus algorithm which handles both Gregorian (post-1582) and Julian (pre-1582) calendar dates automatically.

The calendar reform occurred on October 15, 1582 (Gregorian), which was October 4, 1582 (Julian). Days October 5-14, 1582 don't exist in the Gregorian calendar.
Parameters
- date: CalendarDateTime
  Calendar date and time (can include timezone)
Returns number
Julian Date (fractional days since JD epoch)
See
"Astronomical Algorithms" by Jean Meeus, Chapter 7
Example
```
// J2000.0 epoch: January 1, 2000, 12:00 UTC
toJulianDate({
  year: 2000, month: 1, day: 1,
  hour: 12, minute: 0, second: 0
})
// Returns: 2451545.0
```
Example
```
// With timezone (converted to UTC)
toJulianDate({
  year: 2000, month: 1, day: 1,
  hour: 12, minute: 0, second: 0,
  timezone: -5  // EST
})
// Returns: 2451545.208333... (17:00 UTC)
```
- Defined in time/julian-date.ts:49