Terminal clock with NTP sync bash script

time.sh

#!/bin/bash

tz_hours=0
tz_minutes=0

while [[ $# -gt 0 ]]; do
  case "$1" in
    -h) tz_hours="$2"; shift 2 ;;
    -m) tz_minutes="$2"; shift 2 ;;
    *) exit 1 ;;
  esac
done

tz_offset_seconds=$((tz_hours * 3600 + tz_minutes * 60))

fetch_ntp() {
  msg=$(printf '\x1b\0%.0s' {1..47})
  response=$(echo -ne "$msg" | socat -T 2 - UDP:time.google.com:123 2>/dev/null)
  [[ -z "$response" ]] && return
  hex=$(echo -n "$response" | hexdump -v -e '1/1 "%02x"')
  transmit_ts_hex=${hex:80:8}
  ntp_seconds=$((16#${transmit_ts_hex}))
  unix_seconds=$((ntp_seconds - 2208988800))
  ntp_time=$unix_seconds
  local_time=$(date +%s)
}

print_time() {
  formatted=$(date -u -r "$1" "+%A, %d %B %Y at %I:%M:%S %p")
  echo -e "\033[H\033[J$formatted"
}

fetch_ntp
count=0

while true; do
  now=$(date +%s)
  diff=$((now - local_time))
  current=$((ntp_time + diff + tz_offset_seconds))
  print_time "$current"
  sleep 1
  count=$((count + 1))
  ((count % 60 == 0)) && fetch_ntp
done

bash time.sh -h 5 -m 30