Help with hex editor

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SUPERLINER

5 posts

Wannabe Geek

#228872 26-Jan-2018 14:17

I'm trying to modify hex code in a file that shows a date in a program.
I cannot figure out the code:

a5 c6 = 2017/04/05

3e c8 = 2017/08/14

7b c9 = 2017/11/31

What would be the hex code to display 2017/12/14

Any help greatly appreciated

Rikkitic

Awrrr
17218 posts

Uber Geek

Lifetime subscriber

#1947204 26-Jan-2018 15:11

Your dates don't make sense. Assuming the last figure is the day, and the one before is the month, there are not 31 days in November so the date is impossible. It doesn't work the other way either, since there are not 14 months.

Plesse igmore amd axxept applogies in adbance fir anu typos

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SUPERLINER

5 posts

Wannabe Geek

#1947216 26-Jan-2018 15:49

Correct the date format is indeed YYYY/MM/DD

The 7b c9 was the result of me changing the code and the software displaying 2017/11/31

7a c9 would indeed show 2017/11/30

tchart

2298 posts

Uber Geek

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Trusted

#1947218 26-Jan-2018 15:52

Can you post the results of some sequential dates eg

2017/04/01

2017/04/02

2017/04/03

etc

MurrayM

2319 posts

Uber Geek

ID Verified

#1947219 26-Jan-2018 15:52

https://www.google.com/search?q=encode+date+in+2+bytes

SUPERLINER

5 posts

Wannabe Geek

#1947230 26-Jan-2018 16:13

MurrayM

Ive had a read on a few posts from that google search but unfortunately it's way over my head! Anyway you could help out to give me the hex values to display 2017/12/14

nzkc

1274 posts

Uber Geek

#1947233 26-Jan-2018 16:30

Youre going to need to give us some more examples/data so we can reverse engineer the formula.

I'm going to guess that 5 bits store the day (32 values possible with 5 bits). 4 bits for the month. You then have 7 bits left over for the year. There'd be some epoc date/year for this too. 1950 maybe (you have up to 127 years you could store). Could be 1970. Could be something else entirely.

We know its not storing days since an epoc date and using function to calculate the date from that. Otherwise your single bit change would not have yielded an invalid date. You could try incrementing a bit at a time and see what dates come out. Probably find one or two more increments and either the month or the year would change (it may not be stored as day, month year. Could be day, year, month or any combination of!)

Rikkitic

Awrrr
17218 posts

Uber Geek

Lifetime subscriber

#1947238 26-Jan-2018 16:39

This link might help you.

Plesse igmore amd axxept applogies in adbance fir anu typos

djtOtago

978 posts

Ultimate Geek

#1947246 26-Jan-2018 17:00

Is this some date the program displays when it runs, or are you trying to change some property the program uses?

SUPERLINER

5 posts

Wannabe Geek

#1947251 26-Jan-2018 17:08

This is a date the program displays when it runs

nzkc

1274 posts

Uber Geek

#1948013 29-Jan-2018 08:04

Did a little bit more experimenting....

If you're running Windows open your calculater and set it to programming mode. Then type in the dates in YYYYMMDD format.

The values you gave us earlier then show these "decimal" to hex values:

2017/04/05 => 20170405 = 0x133C6A5

2017/08/14 => 20170814 = 0x133C83E

2017/11/31 => 20171131 = 0x133C97B

2017/11/30 => 20171130 = 0x133C97A

Those are the 4 dates you gave us with corresponding hex values. Observe that the last two bytes are month and day values, with the bytes simply swapped. I think your programme is storing the values as 4 bytes you've only been giving us the last two.

I would then guess your required value for 2017/12/14 is CEC9

Here's the working...

2017/12/14 => 20171214 => 0x133C9CE. Take the last two bytes (C9CE) and swap them to CEC9

SUPERLINER

5 posts

Wannabe Geek

#1948031 29-Jan-2018 09:15

nzkc:

Did a little bit more experimenting....

If you're running Windows open your calculater and set it to programming mode. Then type in the dates in YYYYMMDD format.

The values you gave us earlier then show these "decimal" to hex values:

2017/04/05 => 20170405 = 0x133C6A5

2017/08/14 => 20170814 = 0x133C83E

2017/11/31 => 20171131 = 0x133C97B

2017/11/30 => 20171130 = 0x133C97A

Those are the 4 dates you gave us with corresponding hex values. Observe that the last two bytes are month and day values, with the bytes simply swapped. I think your programme is storing the values as 4 bytes you've only been giving us the last two.

I would then guess your required value for 2017/12/14 is CEC9

Here's the working...

2017/12/14 => 20171214 => 0x133C9CE. Take the last two bytes (C9CE) and swap them to CEC9

You are bang on nzkc, it worked!! I remember experimenting with first byte values with C9 but must not have made it up to CE!

Thank you very much for taking the time to figure that out it will be a huge help both now and in the future, if you were around Wellington I would gladly buy you a beer, cheers!