how encode or decode date in binary

[saykenari]

Hello Friends

I have a problem date format written as DD/MM/YYYY. Date already save into a file as binary. I don't know which technique should be used. Sample date as following


a. 31/09/2009 in binary in the file written as 4f 75 25 00
b. 31/05/2008 in binary in the file written as 5a 74 25 00

My problem is how the date would be written as above in binary. Also, how encode or decode.

Please help me.

Thanks in advance.

[weaknessforcats]

What was the format of the data when it was written?

Was it:

int month
int slash
int day
int slash
int year

??

Or was it:
int month
char slash
int day
char slash
int year

Or was it:

char month
char month
char slash
char day
char day
char slash
char year
char year
char year
char year

??

You can't read file when you don't know the format of the data.

[saykenari]

the date format DD/MM/YYYY meaning

DD -date
slash (/) - just a separator
MM - month
slash (/) - just a separator
YYYY - year

so, data to be taken for decode or encode is DDMMYYYY only

Thanks

[saykenari]

the date format DD/MM/YYYY meaning

DD -date
slash (/) - just a separator
MM - month
slash (/) - just a separator
YYYY - year

so, data to be taken for decode or encode is DDMMYYYY only

Thanks

all data must be in INTEGER example given 31052009

[weaknessforcats]

[quote=saykeenar i]
all data must be in INTEGER example given 31052009
[/code]

If you can read 31052009 in the disc file, then you date is a string of char integers.

Further, it means the file is not in binary. If it was, you couldn't read the data directly with your eye.

From what you say, the disc file is in text mode and you need to read the date into a char array. Then you can parse the array and add the slashes.

[newb16]

all data must be in INTEGER example given 31052009

So, must it be integer (32-bit) 30million-something for day 30 or the same 32 bits in unknown format you gave in first post (4f 75 25 00) ?

[saykenari]

So, must it be integer (32-bit) 30million-something for day 30 or the same 32 bits in unknown format you gave in first post (4f 75 25 00) ?

Yes, this in unsigned integer and using 32 bits to save the data. So, I am not sure how or technique used to encode or decode or using bitwise operator as mentioned in my first post. So,it is the main problem.

I hope you can understand it

Thank you

[newb16]

Yes, this in unsigned integer and using 32 bits to save the data. So, I am not sure how or technique used to encode or decode or using bitwise operator as mentioned in my first post. So,it is the main problem.

I hope you can understand it

Thank you

I understand, but the data provided ( 2 samples ) is not enough to guess how data is encoded, are there any fields where day month and year are stored independently or is it flat ( days since some date ) number.
It seems however that it is low-endian 'days since ***' format ( as first minus second equals 245, that is number of days in year minus 120 days in four months )
So you need to convert it to 32bit integer, find where is zero point of the scale and go.

[saykenari]

I understand, but the data provided ( 2 samples ) is not enough to guess how data is encoded, are there any fields where day month and year are stored independently or is it flat ( days since some date ) number.
It seems however that it is low-endian 'days since ***' format ( as first minus second equals 245, that is number of days in year minus 120 days in four months )
So you need to convert it to 32bit integer, find where is zero point of the scale and go.

Oh , I am forgot that the first date as I mentioned is wrongly typed. The other sample data which same format DDMMYYYY I found as following :

Date : 31012009 written as 4f 75 25 00
Date : 30092009 written as 41 76 25 00
Date : 01122009 written as 7f 76 25 00
Date : 02012010 written as 9f 76 25 00
Date : 30012009 written as 4e 75 25 00
Date : 01012010 written as 9e 76 25 00


So, I am not understand how it got the above. Would you show the calculation to me and to be written in C?

Thank you.

[newb16]

Oh , I am forgot that the first date as I mentioned is wrongly typed. The other sample data which same format DDMMYYYY I found as following :

Date : 31012009 written as 4f 75 25 00
Date : 30092009 written as 41 76 25 00
Date : 01122009 written as 7f 76 25 00
Date : 02012010 written as 9f 76 25 00
Date : 30012009 written as 4e 75 25 00
Date : 01012010 written as 9e 76 25 00


So, I am not understand how it got the above. Would you show the calculation to me and to be written in C?

Thank you.

Do you know how integer numbers are represented in computer?
Open windows calculatorm switch to hex. Enter 25769e( the last number, higher byte is the rightmost), press minus, enter 25754e, press '=', switch to decimal. You get 336, it is exactly a year minus one month, as the second is Dec 1 and the first is Dec 30. So the whole number looks like number of days since some date. If it were bit fields, it probably would have same bits equal if same year/month is equal, that is not this case ( 75-76 transition occurs within the same year ).
To convert it to day, monh and year, you need to find point zero, count leap years correctly (or at least as correct as the program created this format do ) find year, and convert remainder to month and day. I'm not going to do it because *) I have no original program to verify, *)it probably takes more than an hour and *)It is in no way challenging, rewarding or increasing my skills - rather boring and useless, let alone violating Teh Rulz.