Warning : The code is broken due to the forum html bug with some characters

Hi&welcome,

Well to get started that's not an easy task    
Mainly because your date are stored as strings.  

You can use the java Calendar class to use the getTime() method in order to compare two Dates. Like it's shown in this example . You may have to add some additional import statements to let processing know which java classes you are dealing with. Like :

1. import java.util.Calendar;

To set a date in Calendar you can use the method set() with following arguments (or a more precise version if you need time too).

The main difficulty would be to extract the relevant values from your string and put them in the set method (after converted them to int ). You can use regular expressions to do such strings manipulations. Processing allow reg exp trough the use of match() .

If your strings are all the same syntax i've tried to extract day, month and year using a reg exp and that gives :

String date = "Tue, 28 Jun 2009 17:24:09 -0500";
String[] req;

/**
 * (d{1,2}) means match at least one but not more than two digit characters -> day of the month
 * s means drop away the white space character
 * (w{3}) means match exactly three word character -> month formatted as mmm
 * s means as above
 * (d{4}) means match exactly 4 digit characters -> year formmated as yyyy
 */
req = match(date, "(d{1,2})s(w{3})s(d{4})");

for (int i=0; i<req.length; i  ++) {
  println(req[i]);
} I didn't made any check and supposed that your month would always be formatted as 3 characters (Jan, Feb..) and that your Years would be formatted as 4 characters (2011..)

Then you can access to each elements with :

• day,  req[1]
• month, req[2] (need to be converted to a number between 0-12 before use it with calendar)
• year, req[3]

So basically, you need to do that for two dates, creating calendar object containing your date extracted.
And then use the code snippet provided in the javakode link to get the day difference.

  
EDIT : Seems the the forum backslash bug is annoying when trying to using regular expression as it drop double-backslash even using html entity. Any workaround ?
\

It would be more efficient/logical to use DateFormat to parse the textual date...

Thanks for the replies. I tried using SimpleDateFormat from a snippet found here. Unfortunately, I keep getting an "unparseable date" exception:

1. java.text.ParseException: Unparseable date: "Tue, 24 Nov 2009 09:17:34 -0600"
       at java.text.DateFormat.parse(DateFormat.java:337)
       at free_trials_0_2.setup(free_trials_0_2.java:91)
       at processing.core.PApplet.handleDraw(Unknown Source)
       at processing.core.PApplet.run(Unknown Source)
       at java.lang.Thread.run(Thread.java:619)

...any ideas on what's causing this? Here is my code. So far, I'm only trying to convert the date strings to date objects and print successfully:

1. import java.util.Date;
   import java.text.DateFormat;
   import java.text.SimpleDateFormat;
   import java.text.ParseException;
   
   void setup() {
     size(600, 300);
     background(255);
    
     // Import free trial emails line by line
     String[] raw = loadStrings("free_trial.txt");
    
     int[] namecount = new int[raw.length];
     int[] datecount = new int[raw.length];
     int artistNum = 0;
    
     // Fill counts with 0s
     for( int i = 0; i < raw.length; i++ ) {
       namecount[i] = 0;
       datecount[i] = 0;
     }
    
     // Find lines with names and dates
     for( int i = 0; i < raw.length; i++ ) {
       if( raw[i].startsWith("Artist name:") ) {
         namecount[i]++;
       }
       if( raw[i].startsWith("Date:") ) {
         datecount[i]++;
       }
      
       // Count the total number of trial signups
       if( datecount[i] > 0 ) {
         artistNum++;
       }
     }
     println("There are " + artistNum + " total artists");
   
     String[] names = new String[artistNum];
     String[] dates = new String[artistNum];
    
     int j = 0; // Name counter
     int k = 0; // Date counter
     for( int i = 0; i < raw.length; i++ ) {
       if( namecount[i] > 0 ) {
         // Split the line "Artist name: NAME"
         String[] nameChunk = split(raw[i], ": ");
         names[j] = nameChunk[1];
         j++;
       }
       if( datecount[i] > 0 ) {
         // Split the line "Date: DATE"
         String[] dateChunk = split(raw[i], ": ");
         dates[k] = dateChunk[1];
         k++;
       }
     }
    
     Date[] tDates = new Date[artistNum];
    
     for( int i = 0; i < artistNum; i++ ) {
       DateFormat df = new SimpleDateFormat("dd/MM/yyyy");
       try {
         tDates[i] = df.parse(dates[i]);
         println(df.format(tDates[i]));
       } catch (ParseException e) {
         e.printStackTrace();
       }
     }
   }

Thanks!

Actually, I seem to have figured it out. This might be obvious to most, but I only just realized I had to match the input date to the date format I chose. I used splitToken to break the string "Date: Tue, 22 Feb 2011 15:51:12 -0600" into chunks, then reconstructed it into "MMM/dd/yyyy" format. Once the strings were successfully converted to dates, the difference equation worked great:

1.   // dates[i] look like "Jun/15/2010"
     Date[] tDates = new Date[artistNum];
    
     for( int i = 0; i < artistNum; i++ ) {
       DateFormat df = new SimpleDateFormat("MMM/dd/yyyy");
       try {
         tDates[i] = df.parse(dates[i]);
       } catch (ParseException e) {
         e.printStackTrace();
       }
     }
    
     int msPerDay = 1000 * 60 * 60 * 24;
     long firstTime = tDates[artistNum-1].getTime();
     long lastTime = tDates[0].getTime();
     int dif = floor( lastTime/msPerDay ) - floor( firstTime/msPerDay);
     println(dif);

Thanks for the help!

No need to "break in chunks", I pointed to the DateFormat reference precisely to avoid this.
I found the exact date format in the SimpleDateFormat reference, in the examples:

1.   int artistNum = 1;
2.   String[] dates = new String[artistNum];
3.   dates[0] = "Tue, 24 Nov 2009 09:17:34 -0600";
4.   Date[] tDates = new Date[artistNum];
5.   // No need to compute DataFormat on each loop!
6.   DateFormat df = new SimpleDateFormat("EEE, d MMM yyyy HH:mm:ss Z", Locale.US);
7.  
8.   for( int i = 0; i < artistNum; i++ ) {
9.     try {
10.       tDates[i] = df.parse(dates[i]);
11.     } catch (ParseException e) {
12.       e.printStackTrace();
13.       return;
14.     }
15.   }