时间格式的处理

• 儒略日计算

Jul=Julday(month,day,year，hour,minute,second)

• 由儒略日计算date

CALDAT, Jul, Month [, Day [, Year [, Hour [, Minute [, Second]]]]]

• 生成儒略日时间

MyTimes = TIMEGEN(365, UNITS="Days") + SYSTIME(/JULIAN)
MyTimes = TIMEGEN(12, UNITS="Months", START=JULDAY(1,1,2000))

• 画图，时间坐标

label_date

例：  dummy = LABEL_DATE(DATE_FORMAT='%M%Z')
mytimes=timegen(12,unit='months,start=julday(1,1,2012))
y=findgen(12)
plot,mytimes,y,xtickformat='label_date'

DATE_FORMAT 格式
%M for month
%N for month (2 digit abbr)
%D for day of month,
%Y for 4 digit year.
%Z for last two digits of year.
%W for day of week

   For time:
%A for AM or PM
%H for Hours, 2 digits.
%I for minutes, 2 digits.
%S for Seconds, 2 digits.
%0--%9 following %S, indicates digits after decimal point.
%% is %
例子  '%D/%N/%Y' yields 11/12/1993
'%M!C%Y' yields DEC on the top line, 1993 on  the bottom (!C is the new line graphic command).

astro_lib中的儒略日相关程序