Re: EPOCHREALTIME to days, hours, minutes, seconds

[Seth David Schoen]

Alex fxmbsw7 Ratchev writes:

> ~ $ d=$EPOCHREALTIME dd=${d%.*} t=( $( printf '%(%FT%T)T %(%z)T' $dd $dd )
> ) t[1]=${t[1]::3}:${t[1]:3} r=$( date -d "${t[*]}" +%FT%T.${d#*.}%z ) ;
> declare -p r
> declare -- r="2021-08-19T21:55:07.872144+0200"
> 
> On Thu, Aug 19, 2021, 20:38 hancooper via <help-bash@gnu.org> wrote:
> 
> > Is there a neat way to convert from decimal seconds (result from
> > EPOCHREALTIME) to days, hours, minutes, seconds?

If you're looking for an interval (e.g. "4 years") rather than a date
(e.g. "1974-01-01T00:00:00"), then you can start with a value in the
shell variable "seconds" and then do something like

years=$((seconds/31536000))
seconds=$((seconds/31536000))

days=$((seconds/86400))
seconds=$((seconds%86400))

hours=$((seconds/3600))
seconds=$((seconds%3600))

minutes=$((seconds/60))
seconds=$((seconds%60))

Then the shell variables "years", "days", "hours", "minutes", and "seconds"
will contain integers, like

echo "$years years, $days days, $hours hours, $minutes minutes, $seconds 
seconds"

A more concise but harder to read version would be

for scale in 31536000 86400 3600 60; do
  echo -n "$((seconds/scale)) "
  seconds=$((seconds%scale))
done; echo $seconds

A problem here this is that it ignores leap days and leap seconds in
this conversion, meaning that the values that you get this way can't be
directly aligned with a calendar.  (Because precisely how long a "year"
is in seconds really depends on which particular calendar year; there's
no single answer to that question.)  But the values you get from this
calculation would be meaningful to a human reader and can also be
compared with one another, at least!

For a more astronomy-oriented approach you could say that a year is
31556926 seconds instead of 31536000; this is a pretty accurate value on
average in astronomical terms.