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MJDtime: C
library for date-time conversion |
MJDtime current version is 1.05
This is C software for converting
between various UTC date/time formats: Modified Julian Date, Julian Date, NASA
CDF Epoch, ISO time strings and broken down time (year, month, day [or day of
year], hour, minute, second [as a double]). It understands both Julian and
Gregorian calendars and both CE(AD) and BCE(BC) dates.
It can also format the date/time
into a text string using all the format specifiers available in the standard
library strftime() with the same syntax. Additionally it can print decimal
fractions of seconds. It differs from strftime() in that the locale is ignored
and dates and times are always in UTC.
It can also determine the
difference between two date/time structures in either days or seconds as a
double, and provide the day of week and week of year for a specified date.
The default changeover from
Julian to Gregorian Calendar is from 15 October 1582 (Gregorian), but this can
be set by the user in software.
Date and time are stored
internally as a structure holding an integer value for the MJD day and a double
as seconds from the start of this day. The seconds field may be negative or
exceed a full day. Within a day time can be handled down to picosecond
accuracy, but for longer time spans accuracy diminishes. For most applications
Microsecond accuracy is attainable (note that conversion to/from CDF Epoch will
be limited to millisecond accuracy, and Epoch16 is not yet included).
History
03 Feb 2009: v1.01:
Fixes bus error in strfMJD() when
"%." format is used for time with hour,
minute, second all zero.
Also removes trailing space in
getISOString() and improves formatting of "%." and "%{1-9}" in strfMJD().
04 Feb 2009: v1.02:
Changes format in getISOstring()
from %g to %f (change by PLPLOT team).
05 Feb 2009: v1.03:
Fixes getDiffSecs() and getDiffDays().
25 Feb 2009: v1.04:
Incorporates modifications
provided by Alan Irwin of the PLPLOT team.
Allows the user to set the date
for switching between Julian and Gregorian calendars.
03 Mar 2009: v1.05:
Improves formatting of seconds
field by rounding before call to breakDownMJD() in strfMJD().
Obtaining MJDtime
The software source and
documentation are available as a compressed tar file, MJDtime.tar.gz.
Documentation
The routines are described in
detail in
- MJDtime Manual (html)
·
Authors
This software was written by the QSAS team at the Cluster Science Centre, Space and Atmospheric Physics, Imperial College, London.
MJDtime is developed as part of
the Cluster Science Centre within the UK and funded by the Science and
Technology Facilities Council . The software is provided as is under the LGPL public licence,
though IC retains the copyright. No liability is accepted for any damage
resulting from the installation or use of this software, and no guarantee of
its suitability is implied for any use. Copyright.
Send comments and suggestions to csc-support-dl@imperial.ac.uk
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