fix_gpsrollover.py

#!/bin/python

# cat /dev/ttyACM3 | python /home/user/fix_gpsrollover.py | gpsd -n -N /dev/stdin 
# where /dev/ttyACM3 is your gps serial output.

from datetime import datetime, timedelta

import sys
import os
from signal import signal, SIGPIPE, SIG_DFL
signal(SIGPIPE,SIG_DFL) 

separator = ','


def calculate_checksum(nmea_data):
    nmea_data_buffer = ''
    nmea_checksum = 0
    for c in nmea_data:
        if c == '*':
            break
        if c != '$':
            nmea_data_buffer = nmea_data_buffer + c
            nmea_checksum = ord(c) ^ nmea_checksum

    return '$' + nmea_data_buffer + '*' + format(nmea_checksum, 'X') + os.linesep


def write_to_stdout(line):
    sys.stdout.write(line)
    sys.stdout.flush()


for line in iter(sys.stdin.readline, b''):
    if line.startswith('$GPRMC'):
        rmc_data = line.split(separator)
        if len(rmc_data) > 10:
            date = rmc_data[9]
            if date:
              corrected_date = (datetime.strptime(date, '%d%m%y') + timedelta(days=1024*7)).strftime('%d%m%y')
              rmc_data[9] = corrected_date
              rmc_line = calculate_checksum(separator.join(rmc_data))
              write_to_stdout(rmc_line)
              continue
    write_to_stdout(line)