CDF_EPOCH
The
CDF_EPOCH procedure computes or breaks down CDF_EPOCH values in a Common Data Format file. When computing an
epoch, any missing value is considered to be set to zero.
If you supply a value for the
Epoch
argument and set the BREAKDOWN_EPOCH keyword, CDF_EPOCH will compute the values of the
Year
,
Month
,
Day
, etc. and insert the values into the named variables you supply. If you specify the
Year
(and optionally, the
Month
,
Day
, etc.) and set the COMPUTE_EPOCH keyword, CDF_EPOCH will compute the epoch and place the value in the named variable supplied as the
Epoch
parameter.
Calling Sequence
CDF_EPOCH,
Epoch, Year [, Month, Day, Hour, Minute, Second, Milli]
Arguments
Epoch
The Epoch value to be broken down, or a named variable into which the computed epoch will be placed.
The Epoch value is the number of milliseconds since
01-Jan-0000 00:00:00.000
NOTE:
"Year zero" is a convention chosen by NSSDC to measure epoch values. Note that this date is more commonly referred to as 1 BC. Remember that 1 BC was a leap year.
Year
The year (e.g., 1992) or a named variable.
Month
The month (1-12) or a named variable. You can also set the
Month
argument equal to zero, in which case the
Day
argument can take on any value between 1-366; this number is interpreted as the "Day of the Year" rather than a "Day of the Month".
Day
The day (1-31) or a named variable. If the
Month
argument is set equal to zero,
Day
can be set to any value between 1-366.
Hour
The hour (0-23) or a named variable.
Minute
The minute (0-59) or a named variable.
Second
The second (0-59) or a named variable.
Milli
The millisecond (0-999) or a named variable. If
Hour
,
Minute
, and
Second
are all set equal to zero,
Milli
is interpreted as the "Millisecond of the Day" and can be any value between 0-86400000.
Keywords
BREAKDOWN_EPOCH
If this keyword is set,
Epoch
is a value which will broken down and the resulting Year, Month, Day, etc. are returned in the remaining parameters which must be named variables.
COMPUTE_EPOCH
If this keyword is set,
Epoch
is a named variable into which the epoch is placed and the other parameters are values which will be used to compute the epoch.
Example
To compute the epoch value of Septmber 20, 1992 at 3:00 am:
CDF_EPOCH, MergeDate, 1992, 9, 20, 3, /COMPUTE_EPOCH
To break down the given epoch value into standard date components:
CDF_EPOCH, 4.7107656e13, yr, mo, dy, hr, mn, sc, milli, /BREAK
