use command date to convert time format

TLDR - date -j -f '%d/%b/%y' $INPUT_DATE +%Y-%m-%d

• -f takes strftime format string, man strftime
  • turns out python datetime.strftime also uses the exact same format string, because python internally uses standard c library’s strftime
• +%Y-%m-%d is the output format
• -j do not try to set the date, this allows the usage of -f and + to convert one date format to another