extracting datetime from email body

from time import strptime
import datetime
import base64

#code works if the body contains a date stamp using the following format
#  Sat, 7 Jul 2018 19:53:39 -0700 (PDT)
# example body I used started with following string
# Delivered-To: [email protected]\nReceived: by 2002:adf:885c:0:0:0:0:0 with SMTP id e28-v6csp1111454wre;\n        Sat, 7 Jul 2018 19:53:39 -0700 (PDT)

def reverseFind(string, startingIndex, charToFind):
  for i in range(startingIndex-1, 0, -1):
    if string[i] is charToFind:
      return i

def extract_date(decoded_email_body):
  index = reverseFind(decoded_email_body,decoded_email_body.index("(PDT)"), " ")
  last_index = reverseFind(decoded_email_body,index, " ")
  for x in range(0,6):
    index = reverseFind(decoded_email_body,index, " ")
  return decoded_email_body[index+1:last_index]

def convert_datetime_string_to_naive_datetime_object(date_from_email):
  indexBeforeDate = date_from_email.find(" ", 1)
  indexAfterDay = date_from_email.find(" ", indexBeforeDate+ 1)
  day = int(date_from_email[indexBeforeDate+1:indexAfterDay])

  indexAfterMonth = date_from_email.find(" ", indexAfterDay +1)
  month = date_from_email[indexAfterDay+1:indexAfterMonth]
  month = int(strptime(month,'%b').tm_mon)

  indexAfterYear = date_from_email.find(" ", indexAfterMonth + 1)
  year = int(date_from_email[indexAfterMonth+1:indexAfterYear])

  indexAfterHour = date_from_email.find(":", indexAfterYear + 1)
  hour = int(date_from_email[indexAfterYear+1:indexAfterHour])

  indexAfterMinute = date_from_email.find(":", indexAfterHour + 1)
  minute = int(date_from_email[indexAfterHour+1:indexAfterMinute])

  second = int(date_from_email[indexAfterMinute+1:])
  
  return datetime.datetime(year, month, day, hour, minute, second)

body=str(base64.b64decode(body))
date=extract_date(body)
datetime_date=convert_datetime_string_to_naive_datetime_object(date)