Oracle 日期数据类型的范围：“公元前 4712 年 1 月 1 日至公元 9999 年 12 月 31 日”，该范围背后是否有任何逻辑？
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Range for Oracle Date Data Type: "January 1, 4712 BC to December 31, 9999 AD", Does the range has any logic behind it?
提问by Charu
Range for Oracle Date Data Type: "January 1, 4712 BC to December 31, 9999 AD", Does the range has any logic behind it? I mean the range has any historic significance or it has something related to programming and memory size etc. I am just wondering, why only from January 1, 4712 BC to December 31, 9999 AD.
Oracle 日期数据类型的范围：“公元前 4712 年 1 月 1 日至公元 9999 年 12 月 31 日”，该范围背后是否有任何逻辑？我的意思是该范围具有任何历史意义，或者它与编程和内存大小等有关。我只是想知道，为什么只从公元前 4712 年 1 月 1 日到公元 9999 年 12 月 31 日。
采纳答案by Markus Winand
That's the Julian date?
那是朱利安约会？
http://en.wikipedia.org/wiki/Julian_day
http://en.wikipedia.org/wiki/Julian_day
Wikipedia says 4713, hmm...off by 1...
维基百科说 4713，嗯……减 1 分……
I guess the upper limit is just because of the 4 digits.
我猜上限只是因为 4 位数字。
Oracle doc says
甲骨文文档说
http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/datatype.htm#i1847
http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/datatype.htm#i1847
Julian dates allow continuous dating by the number of days from a common reference. (The reference is 01-01-4712 years BCE, so current dates are somewhere in the 2.4 million range.)
儒略日期允许根据共同参考的天数进行连续约会。（参考是公元前 01-01-4712 年，所以当前日期在 240 万年之间。）
EDIT
编辑
I guess the reason for 4712 instead of 4713 is that the conversion requires Y >= -4712:
我猜用 4712 而不是 4713 的原因是转换需要 Y >= -4712：
http://en.wikipedia.org/wiki/Julian_day#Converting_Julian_calendar_date_to_Julian_Day_Number
http://en.wikipedia.org/wiki/Julian_day#Converting_Julian_calendar_date_to_Julian_Day_Number
回答by Erhard Dinhobl
4712: have a look at julian day: http://en.wikipedia.org/wiki/Julian_day#Alternatives
4712：看看朱利安日：http: //en.wikipedia.org/wiki/Julian_day#Alternatives
9999: the highest value presented in 4 digits - at end of this year we will have another "milleniumbug"
9999：4位数的最高值——今年年底我们将迎来另一个“千年虫”
回答by djna
I suspect that it's set the upper limit for ease of formating to the highest 4 digit year, and then deduced the start of range by the capackity of the underlying type.
我怀疑它将易于格式化的上限设置为最高的 4 位年份，然后通过基础类型的容量推断范围的开始。
