+    # Check that between one and two arguments is supplied
+    if ! { [[ $# -ge 1 ]] && [[ $# -le 2 ]]; }; then
+       yell "ERROR:Invalid number of arguments:$# . Exiting.";
+       returnState="error_input"; fi
+
+    # Check that argSeconds provided
+    if [[ $# -ge 1 ]]; then
+       ## Check that argSeconds is a positive integer
+       if [[ "$argSeconds" =~ ^[[:digit:]]+$ ]]; then
+           :
+       else
+           yell "ERROR:argSeconds not a digit.";
+           returnState="error_input";
+       fi
+    else
+       yell "ERROR:No argument provided. Exiting.";
+       exit 1;
+    fi
+
+    # Consider whether argPrecision was provided
+    if  [[ $# -eq 2 ]]; then
+       # Check that argPrecision is a positive integer
+       if [[ "$argPrecision" =~ ^[[:digit:]]+$ ]] && [[ "$argPrecision" -gt 0 ]]; then
+       precision="$argPrecision";
+       else
+           yell "ERROR:argPrecision not a positive integer. (is $argPrecision ). Leaving early.";
+           returnState="error_input";
+       fi;
+    else
+       :
+    fi;
+    
+    remainder="$argSeconds" ; # seconds
+    ## Calculate full years Y, update remainder
+    fullYears=$(( remainder / (365*24*60*60) ));
+    remainder=$(( remainder - (fullYears*365*24*60*60) ));
+    ## Calculate full months M, update remainder
+    fullMonths=$(( remainder / (30*24*60*60) ));
+    remainder=$(( remainder - (fullMonths*30*24*60*60) ));
+    ## Calculate full days D, update remainder
+    fullDays=$(( remainder / (24*60*60) ));
+    remainder=$(( remainder - (fullDays*24*60*60) ));
+    ## Calculate full hours H, update remainder
+    fullHours=$(( remainder / (60*60) ));
+    remainder=$(( remainder - (fullHours*60*60) ));
+    ## Calculate full minutes M, update remainder
+    fullMinutes=$(( remainder / (60) ));
+    remainder=$(( remainder - (fullMinutes*60) ));
+    ## Calculate full seconds S, update remainder
+    fullSeconds=$(( remainder / (1) ));
+    remainder=$(( remainder - (remainder*1) ));
+    ## Check which fields filled
+    if [[ $fullYears -gt 0 ]]; then hasYears="true"; else hasYears="false"; fi
+    if [[ $fullMonths -gt 0 ]]; then hasMonths="true"; else hasMonths="false"; fi
+    if [[ $fullDays -gt 0 ]]; then hasDays="true"; else hasDays="false"; fi
+    if [[ $fullHours -gt 0 ]]; then hasHours="true"; else hasHours="false"; fi
+    if [[ $fullMinutes -gt 0 ]]; then hasMinutes="true"; else hasMinutes="false"; fi
+    if [[ $fullSeconds -gt 0 ]]; then hasSeconds="true"; else hasSeconds="false"; fi
+    
+    ## Determine which fields to display (see ISO-8601:2004 Â§4.4.3.2)
+    witherPrecision="false"
+    
+    ### Years
+    if $hasYears && [[ $precision -gt 0 ]]; then
+       displayYears="true";
+       witherPrecision="true";
+    else
+       displayYears="false";
+    fi;
+    if $witherPrecision; then ((precision--)); fi;
+    
+    ### Months
+    if $hasMonths && [[ $precision -gt 0 ]]; then
+       displayMonths="true";
+       witherPrecision="true";
+    else
+       displayMonths="false";
+    fi;
+    if $witherPrecision && [[ $precision -gt 0 ]]; then
+       displayMonths="true";
+    fi;
+    if $witherPrecision; then ((precision--)); fi;
+
+    ### Days
+    if $hasDays && [[ $precision -gt 0 ]]; then
+       displayDays="true";
+       witherPrecision="true";
+    else
+       displayDays="false";
+    fi;
+    if $witherPrecision && [[ $precision -gt 0 ]]; then
+       displayDays="true";
+    fi;
+    if $witherPrecision; then ((precision--)); fi;
+
+    ### Hours
+    if $hasHours && [[ $precision -gt 0 ]]; then
+       displayHours="true";
+       witherPrecision="true";
+    else
+       displayHours="false";
+    fi;
+    if $witherPrecision && [[ $precision -gt 0 ]]; then
+       displayHours="true";
+    fi;
+    if $witherPrecision; then ((precision--)); fi;
+
+    ### Minutes
+    if $hasMinutes && [[ $precision -gt 0 ]]; then
+       displayMinutes="true";
+       witherPrecision="true";
+    else
+       displayMinutes="false";
+    fi;
+    if $witherPrecision && [[ $precision -gt 0 ]]; then
+       displayMinutes="true";
+    fi;
+    if $witherPrecision; then ((precision--)); fi;
+
+    ### Seconds
+
+    if $hasSeconds && [[ $precision -gt 0 ]]; then
+       displaySeconds="true";
+       witherPrecision="true";
+    else
+       displaySeconds="false";
+    fi;
+    if $witherPrecision && [[ $precision -gt 0 ]]; then
+       displaySeconds="true";
+    fi;
+    if $witherPrecision; then ((precision--)); fi;
+
+    ## Determine whether or not the "T" separator is needed to separate date and time elements
+    if ( $displayHours || $displayMinutes || $displaySeconds); then
+       displayDateTime="true"; else displayDateTime="false"; fi
+    
+    ## Construct duration output string
+    output="P"
+    if $displayYears; then
+       output=$output$fullYears"Y"; fi
+    if $displayMonths; then
+       output=$output$fullMonths"M"; fi
+    if $displayDays; then
+       output=$output$fullDays"D"; fi
+    if $displayDateTime; then
+       output=$output"T"; fi
+    if $displayHours; then
+       output=$output$fullHours"H"; fi
+    if $displayMinutes; then
+       output=$output$fullMinutes"M"; fi
+    if $displaySeconds; then
+       output=$output$fullSeconds"S"; fi
+
+    ## Output duration string to stdout
+    echo "$output" && returnState="true";
+
+    #===Determine function return code===
+    if [ "$returnState" = "true" ]; then
+       return 0;
+    elif [ "$returnState" = "error_input" ]; then
+       yell "ERROR:input";
+       return 1;
+    else
+       yell "ERROR:Unknown";
+       return 2;
+    fi
+
+} # Get duration (ex: PT10M4S )
+timeUntilNextDay(){
+    # Desc: Report seconds until next day.
+    # Version: 1.0.2
+    # Output: stdout: integer seconds until next day
+    # Output: exit code 0 if stdout > 0; 1 if stdout = 0; 2 if stdout < 0
+    # Usage: timeUntilNextDay
+    # Usage: if ! myTTL="$(timeUntilNextDay)"; then yell "ERROR in if statement"; exit 1; fi
+    # Depends: date 8, echo 8, yell, try
+    
+    local returnState timeCurrent timeNextDay secondsUntilNextDay returnState