date variable

Posted on 2004-08-11
Medium Priority
Last Modified: 2010-04-01

I have a series of structs in a program.  One of the structs listed here
//Date struct
struct Date{
      int day;
      int month;
      int year;
requires 2 functions
fileInputDate- to read a date in the format dd/mm/yyyy from a text file and return a variable of type Date.
outputDate- to display a Date variable in an acceptable format.
I need to know what type of data is best to use for the date variable.


Question by:KazIT
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LVL 11

Expert Comment

ID: 11781448
guess your structure is good enough for date

though you can make them as unsigned ints.

as in
struct date{
     unsigned int day;
    unsigned int month;
     unsigned int year;

depending on your needs you may also decide to use enum data types for those

LVL 11

Expert Comment

ID: 11781841
to save some memory you could set your variables to:

struct date{
   short unsigned int day;
   short unsigned int month;
   short  unsigned int year;
LVL 16

Expert Comment

ID: 11781862
or even

struct date{
   unsigned char day;
   unsigned char month;
   unsigned short year;
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LVL 39

Expert Comment

ID: 11782700
I prefer to have an integer date yyyymmdd as data member like that:

class Date
     int date;
     Date(const string& strDate) : date(0)
          int d, m, y;
          istringstream istr(strDate);
          istr >> d; if (istr.fail()) return;
          istr >> m; if (istr.fail()) return;    
          istr >> y; if (istr.fail()) return;  
          y = (y < 50)? 2000+y : (y < 100)? 1900 + y : y;
          if ((y < 1000 || y > 2200) ||
              (m < 1    || m > 12  ) ||
              (d < 1    || d > 31  ) ||
              (d == 31 && 
                (m == 4 || m == 6 || m == 9 || m == 11)
              )                      ||
              (m == 2 && 
                 (d > 28 + leap(y) )
          date = y*10000 + m*100 + d;
     int leap(int y) { return ((y % 4) == 0 && ((y % 100) != 0 || (y % 400) == 0))? 1 : 0; }
     bool isValidDate() { return date != 0; }
     string getDateAsString()
     {   stringstream ss;
          ss << date % 100 << '/' << (date%10000) / 100 << '/' << date/10000;
          return ss.str();

Regards, Alex

LVL 86

Expert Comment

ID: 11784236
>>I need to know what type of data is best to use for the date variable.

Use what the C/C++ runtime libraries use - a 'time_t', which is nothing but a 'long int'.
LVL 39

Expert Comment

ID: 11784338
>> Use what the C/C++ runtime libraries use - a 'time_t'

time_t is the number of seconds elapsed since midnight (00:00:00), January 1, 1970, so i wouldn't recommend it for a Date class.

Regards, Alex
LVL 86

Expert Comment

ID: 11784362
Why not? The date is included. And, it only uses 4 bytes of space. Since all POSIX conformant systems rely on that...
LVL 39

Accepted Solution

itsmeandnobodyelse earned 2000 total points
ID: 11784422
>> The date is included

But my birthday couldn't be stored with that ... ;-)

>> Since all POSIX conformant systems

All younger than me ...

Regards, Alex


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