$duration() works for that.

//echo Seconds 90, translates to $duration(90)

Would echo "Seconds 90, translates to 1min 30secs"

Somewhat on topic, and more of a "Just for your information." You could easily script your own, by doing something like this.

Code:
alias sec2dur {
  var %secs = $1
  var %weeks = $int($calc(%secs / $calc(60*60*24*7)))
  var %secs = $calc(%secs % $calc(60*60*24*7))
  var %days = $int($calc(%secs / $calc(60*60*24)))
  var %secs = $calc(%secs % $calc(60*60*24))
  var %hours = $int($calc(%secs / $calc(60*60)))
  var %secs = $calc(%secs % $calc(60*60))
  var %min = $int($calc(%secs / 60))
  var %secs = $calc(%secs % 60)
  echo -a $iif(%weeks,$v1 weeks) $iif(%days,$v1 days) $iif(%hours,$v1 hours) $iif(%min,$v1 minutes) $iif(%secs,$v1 seconds)
}