Finding timestamp in hex data

Question

I'm reading stuff from public transport cards and I've got this hex data which is an usage history. I believe that these records contain timestamp or date in some format (but I'm not sure), but I haven't found where and in what format.

                                                    DD.MM.YYYY HH:MM
e1 a2 00 00 ce 04 85 93 7e 00 78 17 0a 10 00 f8     26.02.2014 22:47
e1 a2 00 00 ce 04 05 b1 7e 00 68 22 0a 10 00 ce     01.03.2014 19:40
e4 a2 00 00 ce 04 e5 7b 7e 00 e4 2e 0a 10 00 e9     01.03.2014 23:36
e4 a2 00 00 4c 04 43 8c d0 07 30 00 01 00 00 72     04.03.2014 16:31
e4 a2 00 00 ce 04 65 8d 7e 00 7c 17 0a 10 00 a2     04.03.2014 18:51
ea a2 00 00 ce 04 25 63 7e 00 70 09 0a 10 00 f1     10.03.2014 13:13
ec a2 00 00 ce 04 25 63 7e 00 70 09 0a 10 00 da     12.03.2014 13:13
         |
 This is always zero

Any help is appreciated.

Answer 1

Just some random thoughts after going over the given data:

• What did you do so far to figure out the format?
• Where do you get the DD.MM.YYYY HH:MM formatted text from?
• Is the given data guaranteed to be correct? It seems the fourth row does not match with the others? More data would possible simplify the format analysis.
• The last byte may be a CRC.
• The second nibble of the first byte may be related to day for row 2, 4, 5, 6, 7. This may be false as it does not hold up for all rows. However, given the fact that the 6th and 7th row only differ at the first byte it is possibly related, assuming the last byte is a CRC.