Date and Time Formatting Examples

Contents

1. Format
   1. C++
   2. C
2. Parse
   1. C++
   2. C
   3. Java
3. Getting Specific Date Fields
   1. C++
   2. C
4. DateTimePatternGenerator
   1. Java
   2. C++
   3. C
5. Changing the TimeZone Formatting Style
   1. Java

---

Format

The ICU DateFormat interface enables you to format a date in milliseconds into a string representation of the date. Also, the interface enables you to parse the string back to the internal date representation in milliseconds.

C++

DateFormat* df = DateFormat::createDateInstance();
UnicodeString myString;
UDate myDateArr[] = { 0.0, 100000000.0, 2000000000.0 }; 
for (int32_t i = 0; i < 3; ++i) {
 myString.remove();
 cout << df->format( myDateArr[i], myString ) << endl;
}

C

/* 1st example: format the dates in millis 100000000 and 2000000000 */
UErrorCode status=U_ZERO_ERROR;
int32_t i, myStrlen=0;
UChar* myString;
UDate myDateArr[] = { 0.0, 100000000.0, 2000000000.0 }; // test values
UDateFormat* df = udat_open(UCAL_DEFAULT, UCAL_DEFAULT, NULL, "GMT", &status);
for (i = 0; i < 3; ++i) {
 myStrlen = udat_format(df, myDateArr[i], NULL, myStrlen, NULL, &status);
 if(status==U_BUFFER_OVERFLOW_ERROR){
 status=U_ZERO_ERROR;
 myString=(UChar*)malloc(sizeof(UChar) * (myStrlen+1) );
 udat_format(df, myDateArr[i], myString, myStrlen+1, NULL, &status);
 printf("%s\n", austrdup(myString) ); 
 /* austrdup( a function used to convert UChar* to char*) */
 free(myString);
 }
}

Parse

To parse a date for a different locale, specify it in the locale call. This call creates a formatting object.

C++

DateFormat* df = DateFormat::createDateInstance
 ( DateFormat::SHORT, Locale::getFrance());

C

/* 2nd example: parse a date with short French date/time formatter */
UDateFormat* df = udat_open(UDAT_SHORT, UDAT_SHORT, "fr_FR", "GMT", &status);
UErrorCode status = U_ZERO_ERROR;
int32_t parsepos=0; 
UDate myDate = udat_parse(df, myString, u_strlen(myString), &parsepos,
&status);

Java

import java.text.FieldPosition;
import java.text.ParseException;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;
import com.ibm.icu.text.DateFormat;
public class TestDateTimeFormat {
 public void run() {
 // Formatting Dates
 DateFormat dfUS = DateFormat.getDateInstance(DateFormat.FULL, Locale.US);
 DateFormat dfFrance = DateFormat.getDateInstance(DateFormat.FULL, Locale.FRANCE);
 StringBuffer sb = new StringBuffer();
 Calendar c = Calendar.getInstance();
 Date d = c.getTime();
 sb = dfUS.format(d, sb, new FieldPosition(0));
 System.out.println(sb.toString());
 StringBuffer sbf = new StringBuffer();
 sbf = dfFrance.format(d, sbf, new FieldPosition(0));
 System.out.println(sbf.toString());
 StringBuffer sbg = new StringBuffer();
 DateFormat dfg = DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.SHORT);
 FieldPosition pos = new FieldPosition(DateFormat.MINUTE_FIELD);
 sbg = dfg.format(d, sbg, pos);
 System.out.println(sbg.toString());
 System.out.println(sbg.toString().substring(pos.getBeginIndex(), pos.getEndIndex()));
 // Parsing Dates
 String dateString_US = "Thursday, February 7, 2008";
 String dateString_FRANCE = "jeudi 7 février 2008";
 try {
 Date parsedDate_US = dfUS.parse(dateString_US);
 Date parsedDate_FRANCE = dfFrance.parse(dateString_FRANCE);
 System.out.println(parsedDate_US.toString());
 System.out.println(parsedDate_FRANCE.toString());
 } catch (ParseException pe) {
 System.out.println("Exception while parsing :" + pe);
 }
 }
 public static void main(String args[]) {
 new TestDateTimeFormat().run();
 }
}

Getting Specific Date Fields

To get specific fields of a date, you can use the FieldPosition function for C++ or UFieldPosition function for C.

C++

UErrorCode status = U_ZERO_ERROR;
FieldPosition pos(DateFormat::YEAR_FIELD)
UDate myDate = Calendar::getNow();
UnicodeString str;
DateFormat* df = DateFormat::createDateInstance
 ( DateFormat::LONG, Locale::getFrance());
df->format(myDate, str, pos, status);
cout << pos.getBeginIndex() << "," << pos. getEndIndex() << endl;

C

UErrorCode status = U_ZERO_ERROR;
UFieldPosition pos;
UChar *myString;
int32_t myStrlen = 0;
char buffer[1024];
pos.field = 1; /* Same as the DateFormat::EField enum */
UDateFormat* dfmt = udat_open(UCAL_DEFAULT, UCAL_DEFAULT, NULL, "PST",
&status);
myStrlen = udat_format(dfmt, myDate, NULL, myStrlen, &pos, &status);
if (status==U_BUFFER_OVERFLOW_ERROR){
 status=U_ZERO_ERROR;
 myString=(UChar*)malloc(sizeof(UChar) * (myStrlen+1) );
 udat_format(dfmt, myDate, myString, myStrlen+1, &pos, &status);
}
printf("date format: %s\n", u_austrcpy(buffer, myString));
buffer[pos.endIndex] = 0; // NULL terminate the string.
printf("UFieldPosition position equals %s\n", &buffer[pos.beginIndex]);

DateTimePatternGenerator

This class lets you get a different variety of patterns, such as month+day. The following illustrates this in Java, C++ and C.

Java

// set up the generator
DateTimePatternGenerator generator
 = DateTimePatternGenerator.getInstance(locale);
// get a pattern for an abbreviated month and day
final String pattern = generator.getBestPattern("MMMd");
SimpleDateFormat formatter = new SimpleDateFormat(pattern, locale);
// use it to format (or parse)
String formatted = formatter.format(new Date());
// for French, the result is "13 sept."

C++

// set up the generator
status = U_ZERO_ERROR;
DateTimePatternGenerator *generator = DateTimePatternGenerator::createInstance( locale, status);
if (U_FAILURE(status)) {
 return;
}
 
// get a pattern for an abbreviated month and day
UnicodeString pattern = generator->getBestPattern(UnicodeString("MMMd"), status); 
SimpleDateFormat *formatter = new SimpleDateFormat(pattern, locale, status); 
// use it to format (or parse)
UnicodeString formatted;
formatted = formatter->format(Calendar::getNow(), formatted, status); 
// for French, the result is "13 sept."

C

const UChar skeleton[]= {'M', 'M', 'M', 'd', 0};
status=U_ZERO_ERROR; 
generator=udatpg_open(locale, &status);
if(U_FAILURE(status)) {
 return;
}
/* get a pattern for an abbreviated month and day */
length = udatpg_getBestPattern(generator, skeleton, 4,
 pattern, patternCapacity, &status);
formatter = udat_open(UDAT_IGNORE, UDAT_DEFAULT, locale, NULL, -1, 
 pattern, length, &status);
/* use it to format (or parse) */
formattedCapacity = (int32_t)(sizeof(formatted)/sizeof((formatted)[0]));
resultLen=udat_format(formatter, ucal_getNow(), formatted, formattedCapacity,
 NULL, &status);
/* for French, the result is "13 sept." */

Changing the TimeZone Formatting Style

It also contains some helper functions for parsing patterns. Here’s an example of replacing the kind of timezone used in a pattern.

Java

/**
 * Replace the zone string with a different type, eg v's for z's, etc.
 * <p>Called with a pattern, such as one gotten from 
 * <pre>
 * String pattern = ((SimpleDateFormat)
 * DateFormat.getTimeInstance(style, locale)).toPattern();
 * </pre>
 * @param pattern original pattern to change, such as "HH:mm zzzz"
 * @param newZone Must be: z, zzzz, Z, ZZZZ, v, vvvv, V, or VVVV
 * @return
 */
public String replaceZoneString(String pattern, String newZone) {
 DateTimePatternGenerator.FormatParser formatParser =
 new DateTimePatternGenerator.FormatParser();
 final List itemList = formatParser.set(pattern).getItems();
 boolean found = false;
 for (int i = 0; i < itemList.size(); ++i) {
 Object item = itemList.get(i);
 if (item instanceof VariableField) {
 // the first character of the variable field determines the type,
 // according to CLDR.
 String variableField = item.toString();
 switch (variableField.charAt(0)) {
 case 'z': case 'Z': case 'v': case 'V':
 if (!variableField.equals(newZone)) {
 found = true;
 itemList.set(i, new VariableField(newZone));
 }
 break;
 }
 }
 }
 return found ? formatParser.toString() : pattern;
}