Convert MITgcm iteration number to a date

ts2dte

#!/bin/bash
# Help message function
print_help() {
        echo "Convert MITgcm iteration number to a date."
        echo "written by: Poinelli, Mattia"
        echo "Jet Propulsion Laboratory"
        echo "April, 2024"
        echo
        echo "Based on ts2dte.m in mitgcm/utils/matlab"
        echo
        echo "Usage:"
        echo " ts2dte <ts> <deltat> <startyr> <startmo> <startdy> <form>"
        echo
        echo "Input:"
        echo "ts       time step number"
        echo "deltat   time step length in s (default 1200)"
        echo "startyr  start year (default 1992)"
        echo "startmo  start month (default 1)"
        echo "startdy  start day (default 1)"
        echo "form     format of date"
        echo
        echo "Example:"
        echo "ts2dte 1000 10 2010 2 4"
        echo "returns: Thu Feb  4 02:46:40 PST 2010"

exit 0
}

# Parse command line arguments
if [[ $# -lt 1 ]]; then
  print_help
fi

# Default values
ts="$1"
deltat="${2:-1200}"
startyr="${3:-1992}"
startmo="${4:-1}"
startdy="${5:-1}"
form="$6"

# Calculate the number of seconds to add to the start date
seconds=$((ts * deltat))

# Format the start date
start_date="$startyr-$startmo-$startdy"

# Calculate the final date by adding the seconds to the start date
final_date=$(date -d "$start_date + $seconds seconds")

# Format the final date according to the provided format string
if [ -z "$form" ]; then
  echo "$final_date"
else
  echo "$final_date" | date "+$form"
fi