Changes between Initial Version and Version 1 of TimeFields

Timestamp:

Oct 19, 2009, 5:50:05 PM (17 years ago)

Author:

eugene

Comment:

--

TimeFields

@@ +1 @@
+== Time Fields in DVO ==
+
+mextract and imextract both have fields which represent a time value.  When extracting these fields into vectors, the user has options to control the units and format of the resulting vectors.  The vector is a floating-point value, with a reference date define by the DVO variable $TIMEREF.  The units of the vector may be one of the following values: sec, min, hours, days (note that 'seconds' and 'minutes' invalid and are silently ignored).  
+
+If TIMEREF is not set, it defaults to 1970/01/01,00:00:00.  Some examples of TIMEREF:
+
+{{{
+$TIMEREF = 2001/01/01,00:00:00
+$TIMEREF = 2009/07/01,00:00:00
+}}}
+
+There are two special words for TIMEREF: 'now' and 'today'.  The value of 'now' make the reference the time of the query; the value of 'today' make the reference UT midnight of the day of the query.
+
+Be careful when you set TIMEREF.  if you just do:  $TIMEREF =
+2001/01/01, it will treat that as a math expression, and set the
+reference to 2001 seconds since 1970/01/01...
+
+There are two special words for TIMEFORMAT: 'jd' and 'mjd'.  With these options, TIMEREF is ignored and the date is returned as a JD or MJD.
+
+The dvo (or mana, etc) function 'ctimes' allows for on-the-fly conversions between human readable time/date values and the formated values.  for example:
+{{{
+dvo: $TIMEREF = 2009/10/20,00
+dvo: echo $TIMEREF
+2009/10/20,00
+
+dvo: ctimes -ref 0.0
+time: 2009/10/20,00:00:00
+
+dvo: $TIMEFORMAT = sec
+dvo: ctimes -abs 2009/10/20,01:00:00
+time: 3600.000000
+
+dvo: $TIMEFORMAT = min
+dvo: ctimes -abs 2009/10/20,01:00:00
+time: 60.000000
+
+dvo: $TIMEFORMAT = hours
+dvo: ctimes -abs 2009/10/20,01:00:00
+time: 1.000000
+
+dvo: $TIMEFORMAT = days
+dvo: ctimes -abs 2009/10/20,01:00:00
+time: 0.041667
+
+dvo: $TIMEFORMAT = jd
+dvo: ctimes -abs 2009/10/20,01:00:0
+time: 2455124.541667
+
+dvo: $TIMEFORMAT = mjd
+dvo: ctimes -abs 2009/10/20,01:00:0
+}}}
+