signalk-datetime

SignalK Node Server Plugin that maps the output of the Linux date command to a Signal K path.

This plugin periodically executes the date command (every Update rate seconds) and writes the stdout to the user defined Signal K path. The plugin accepts formatting options (hints below) to allow the user to define exactly how they would like the value to appear (useful for direct display on a dashboard). Additionally, the format options field can be set to the string null to display the default output style that resembles "Wed 15 Sep 2021 08:17:10 AM PDT".

By default, the plugin outputs local 24-hour time like 13:52:10 to the conventional Signal K path environment.time once per second. https://signalk.org/specification/1.5.0/doc/vesselsBranch.html#vesselsregexpenvironmenttime

Date/Time Formatting Options

https://man7.org/linux/man-pages/man1/date.1.html

       FORMAT controls the output.  Interpreted sequences are:

       %%     a literal %

       %a     locale's abbreviated weekday name (e.g., Sun)

       %A     locale's full weekday name (e.g., Sunday)

       %b     locale's abbreviated month name (e.g., Jan)

       %B     locale's full month name (e.g., January)

       %c     locale's date and time (e.g., Thu Mar  3 23:05:25 2005)

       %C     century; like %Y, except omit last two digits (e.g., 20)

       %d     day of month (e.g., 01)

       %D     date; same as %m/%d/%y

       %e     day of month, space padded; same as %_d

       %F     full date; like %+4Y-%m-%d

       %g     last two digits of year of ISO week number (see %G)

       %G     year of ISO week number (see %V); normally useful only
              with %V

       %h     same as %b

       %H     hour (00..23)

       %I     hour (01..12)

       %j     day of year (001..366)

       %k     hour, space padded ( 0..23); same as %_H

       %l     hour, space padded ( 1..12); same as %_I

       %m     month (01..12)

       %M     minute (00..59)

       %n     a newline

       %N     nanoseconds (000000000..999999999)

       %p     locale's equivalent of either AM or PM; blank if not known

       %P     like %p, but lower case

       %q     quarter of year (1..4)

       %r     locale's 12-hour clock time (e.g., 11:11:04 PM)

       %R     24-hour hour and minute; same as %H:%M

       %s     seconds since 1970-01-01 00:00:00 UTC

       %S     second (00..60)

       %t     a tab

       %T     time; same as %H:%M:%S

       %u     day of week (1..7); 1 is Monday

       %U     week number of year, with Sunday as first day of week
              (00..53)

       %V     ISO week number, with Monday as first day of week (01..53)

       %w     day of week (0..6); 0 is Sunday

       %W     week number of year, with Monday as first day of week
              (00..53)

       %x     locale's date representation (e.g., 12/31/99)

       %X     locale's time representation (e.g., 23:13:48)

       %y     last two digits of year (00..99)

       %Y     year

       %z     +hhmm numeric time zone (e.g., -0400)

       %:z    +hh:mm numeric time zone (e.g., -04:00)

       %::z   +hh:mm:ss numeric time zone (e.g., -04:00:00)

       %:::z  numeric time zone with : to necessary precision (e.g.,
              -04, +05:30)

       %Z     alphabetic time zone abbreviation (e.g., EDT)

       By default, date pads numeric fields with zeroes.  The following
       optional flags may follow '%':

       -      (hyphen) do not pad the field

       _      (underscore) pad with spaces

       0      (zero) pad with zeros

       +      pad with zeros, and put '+' before future years with >4
              digits

       ^      use upper case if possible

       #      use opposite case if possible

       After any flags comes an optional field width, as a decimal
       number; then an optional modifier, which is either E to use the
       locale's alternate representations if available, or O to use the
       locale's alternate numeric symbols if available.

Future Ideas and Considerations

• If the vessel is equipped with GPS and already has time and date from GNSS positioning system, perhaps we could subscribe to that path and remap the ISO 8601 datetime string value to a new user-definable path with the applied formatting.
• Both GNSS positioning system time and Linux date can be used together, with the preferred source definable by the user.