to_date 'J' format misunderstanding

In Table 9-22. Template Patterns for Date/Time Formatting we have

'J Julian Day (days since November 24, 4714 BC at midnight)'

But there is no any information about what calender use for date of
November 24, 4714 BC. From wikipedia we know that it is
November 24, 4714 BC, in the proleptic Gregorian calendar.
I think information about Gregorian calendar must include in
documentation for misunderstaning exclusion

PS. In oracle docs we have following info about formatting:

' J Yes Julian day; the number of days since January 1, 4712 BC. Number
specified with J must be integers.'

again no any information about what calendar is using for date January
1, 4712 BC %)

--
Alex Ignatov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company