Say I have a string
"1974-03-20 00:00:00.000"
It is created using DateTime.now(),
how do I convert the string back to a DateTime object?
DateTime has a parse method
var parsedDate = DateTime.parse('1974-03-20 00:00:00.000');
https://api.dartlang.org/stable/dart-core/DateTime/parse.html
There seem to be a lot of questions about parsing timestamp strings into DateTime. I will try to give a more general answer so that future questions can be directed here.
Your timestamp is in an ISO format. Examples: 1999-04-23, 1999-04-23 13:45:56Z, 19990423T134556.789. In this case, you can use DateTime.parse or DateTime.tryParse. (See the DateTime.parse documentation for the precise set of allowed inputs.)
Your timestamp is in a standard HTTP format. Examples: Fri, 23 Apr 1999 13:45:56 GMT, Friday, 23-Apr-99 13:45:56 GMT, Fri Apr 23 13:45:56 1999. In this case, you can use dart:io's HttpDate.parse function.
Your timestamp is in some local format. Examples: 23/4/1999, 4/23/99, April 23, 1999. You can use package:intl's DateFormat class and provide a pattern specifying how to parse the string:
import 'package:intl/intl.dart';
...
var dmyString = '23/4/1999';
var dateTime1 = DateFormat('d/M/y').parse(dmyString);
var mdyString = '04/23/99';
var dateTime2 = DateFormat('MM/dd/yy').parse(mdyString);
var mdyFullString = 'April 23, 1999';
var dateTime3 = DateFormat('MMMM d, y', 'en_US').parse(mdyFullString));
See the DateFormat documentation for more information about the pattern syntax.
DateFormat limitations:
DateFormat cannot parse dates that lack explicit field separators. For such cases, you can resort to using regular expressions (see below).
Prior to version 0.17.0 of package:intl, yy did not follow the -80/+20 rule that the documentation describes for inferring the century, so if you use a 2-digit year, you might need to adjust the century afterward.
As of writing, DateFormat does not support time zones. If you need to deal with time zones, you will need to handle them separately.
Last resort: If your timestamps are in a fixed, known, numeric format, you always can use regular expressions to parse them manually:
var dmyString = '23/4/1999';
var re = RegExp(
r'^'
r'(?<day>[0-9]{1,2})'
r'/'
r'(?<month>[0-9]{1,2})'
r'/'
r'(?<year>[0-9]{4,})'
r'$',
);
var match = re.firstMatch(dmyString);
if (match == null) {
throw FormatException('Unrecognized date format');
}
var dateTime4 = DateTime(
int.parse(match.namedGroup('year')!),
int.parse(match.namedGroup('month')!),
int.parse(match.namedGroup('day')!),
);
See https://stackoverflow.com/a/63402975/ for another example.
(I mention using regular expressions for completeness. There are many more points for failure with this approach, so I do not recommend it unless there's no other choice. DateFormat usually should be sufficient.)
import 'package:intl/intl.dart';
DateTime brazilianDate = new DateFormat("dd/MM/yyyy").parse("11/11/2011");
you can just use : DateTime.parse("your date string");
for any extra formating, you can use "Intl" package.
void main() {
var dateValid = "30/08/2020";
print(convertDateTimePtBR(dateValid));
}
DateTime convertDateTimePtBR(String validade)
{
DateTime parsedDate = DateTime.parse('0001-11-30 00:00:00.000');
List<String> validadeSplit = validade.split('/');
if(validadeSplit.length > 1)
{
String day = validadeSplit[0].toString();
String month = validadeSplit[1].toString();
String year = validadeSplit[2].toString();
parsedDate = DateTime.parse('$year-$month-$day 00:00:00.000');
}
return parsedDate;
}
a string can be parsed to DateTime object using Dart default function DateTime.parse("string");
final parsedDate = DateTime.parse("1974-03-20 00:00:00.000");
Example on Dart Pad
String dateFormatter(date) {
date = date.split('-');
DateFormat dateFormat = DateFormat("yMMMd");
String format = dateFormat.format(DateTime(int.parse(date[0]), int.parse(date[1]), int.parse(date[2])));
return format;
}
I solved this by creating, on the C# server side, this attribute:
using Newtonsoft.Json.Converters;
public class DartDateTimeConverter : IsoDateTimeConverter
{
public DartDateTimeConverter()
{
DateTimeFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss.FFFFFFK";
}
}
and I use it like this:
[JsonConverter(converterType: typeof(DartDateTimeConverter))]
public DateTimeOffset CreatedOn { get; set; }
Internally, the precision is stored, but the Dart app consuming it gets an ISO8601 format with the right precision.
HTH
Related
I am storing a date string in SharedPreferences as 2022-9-14 19:34, but this is not recognized as DateTime when using
DateTime dt1 = DateTime.parse(_inicio);
print("fecha······· ${(dt1)}");
I am getting the following error:
Invalid date format
2022-9-14 19:34
What I need is to show the date string as 14-09-2022 19:34
EDIT
The date string is saved as follows:
var hoy = DateTime.now();
var ano = hoy.year.toString();
var mes = hoy.month.toString();
var dia = hoy.day.toString();
var turno = "";
var fechaHora = ano+"-"+mes+"-"+dia+" "+_timeOfDay.format(context).toString();
And _timeOfDay is the picked time from TimePicker.
2022-09-14 19:34 is one of the valid case. So you need to add zeros where there is a single digit (month in this case)
But a better solution would be to store DateTime.now().toString() directly in shared-preferences. You could also use a package like intl to format the date in your choice of format.
Since you're using time as well from timepicker, you could use DateTime constructor will all 5 values like this:
new DateTime(year, month, date, hour, minute).toString();
Say I have a string
"1974-03-20 00:00:00.000"
It is created using DateTime.now(),
how do I convert the string back to a DateTime object?
DateTime has a parse method
var parsedDate = DateTime.parse('1974-03-20 00:00:00.000');
https://api.dartlang.org/stable/dart-core/DateTime/parse.html
There seem to be a lot of questions about parsing timestamp strings into DateTime. I will try to give a more general answer so that future questions can be directed here.
Your timestamp is in an ISO format. Examples: 1999-04-23, 1999-04-23 13:45:56Z, 19990423T134556.789. In this case, you can use DateTime.parse or DateTime.tryParse. (See the DateTime.parse documentation for the precise set of allowed inputs.)
Your timestamp is in a standard HTTP format. Examples: Fri, 23 Apr 1999 13:45:56 GMT, Friday, 23-Apr-99 13:45:56 GMT, Fri Apr 23 13:45:56 1999. In this case, you can use dart:io's HttpDate.parse function.
Your timestamp is in some local format. Examples: 23/4/1999, 4/23/99, April 23, 1999. You can use package:intl's DateFormat class and provide a pattern specifying how to parse the string:
import 'package:intl/intl.dart';
...
var dmyString = '23/4/1999';
var dateTime1 = DateFormat('d/M/y').parse(dmyString);
var mdyString = '04/23/99';
var dateTime2 = DateFormat('MM/dd/yy').parse(mdyString);
var mdyFullString = 'April 23, 1999';
var dateTime3 = DateFormat('MMMM d, y', 'en_US').parse(mdyFullString));
See the DateFormat documentation for more information about the pattern syntax.
DateFormat limitations:
DateFormat cannot parse dates that lack explicit field separators. For such cases, you can resort to using regular expressions (see below).
Prior to version 0.17.0 of package:intl, yy did not follow the -80/+20 rule that the documentation describes for inferring the century, so if you use a 2-digit year, you might need to adjust the century afterward.
As of writing, DateFormat does not support time zones. If you need to deal with time zones, you will need to handle them separately.
Last resort: If your timestamps are in a fixed, known, numeric format, you always can use regular expressions to parse them manually:
var dmyString = '23/4/1999';
var re = RegExp(
r'^'
r'(?<day>[0-9]{1,2})'
r'/'
r'(?<month>[0-9]{1,2})'
r'/'
r'(?<year>[0-9]{4,})'
r'$',
);
var match = re.firstMatch(dmyString);
if (match == null) {
throw FormatException('Unrecognized date format');
}
var dateTime4 = DateTime(
int.parse(match.namedGroup('year')!),
int.parse(match.namedGroup('month')!),
int.parse(match.namedGroup('day')!),
);
See https://stackoverflow.com/a/63402975/ for another example.
(I mention using regular expressions for completeness. There are many more points for failure with this approach, so I do not recommend it unless there's no other choice. DateFormat usually should be sufficient.)
import 'package:intl/intl.dart';
DateTime brazilianDate = new DateFormat("dd/MM/yyyy").parse("11/11/2011");
you can just use : DateTime.parse("your date string");
for any extra formating, you can use "Intl" package.
void main() {
var dateValid = "30/08/2020";
print(convertDateTimePtBR(dateValid));
}
DateTime convertDateTimePtBR(String validade)
{
DateTime parsedDate = DateTime.parse('0001-11-30 00:00:00.000');
List<String> validadeSplit = validade.split('/');
if(validadeSplit.length > 1)
{
String day = validadeSplit[0].toString();
String month = validadeSplit[1].toString();
String year = validadeSplit[2].toString();
parsedDate = DateTime.parse('$year-$month-$day 00:00:00.000');
}
return parsedDate;
}
a string can be parsed to DateTime object using Dart default function DateTime.parse("string");
final parsedDate = DateTime.parse("1974-03-20 00:00:00.000");
Example on Dart Pad
String dateFormatter(date) {
date = date.split('-');
DateFormat dateFormat = DateFormat("yMMMd");
String format = dateFormat.format(DateTime(int.parse(date[0]), int.parse(date[1]), int.parse(date[2])));
return format;
}
I solved this by creating, on the C# server side, this attribute:
using Newtonsoft.Json.Converters;
public class DartDateTimeConverter : IsoDateTimeConverter
{
public DartDateTimeConverter()
{
DateTimeFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss.FFFFFFK";
}
}
and I use it like this:
[JsonConverter(converterType: typeof(DartDateTimeConverter))]
public DateTimeOffset CreatedOn { get; set; }
Internally, the precision is stored, but the Dart app consuming it gets an ISO8601 format with the right precision.
HTH
I have a date-time in epoch format: 1633247247
I want to convert it into timestamps like this: Sunday, 3 October 2021 or just October 3 2021
I am writing this code
final DateTime timeStamp = DateTime.fromMillisecondsSinceEpoch(1633247247);
But it is returning 1970-01-19 18:25:11.247
Edit I ran this code
final DateTime timeStamp = DateTime.fromMillisecondsSinceEpoch(1633247247 * 1000);
Got the output in datetime. I am now trying to convert into string
String formattedDate = DateFormat('yyyy-MM-dd – kk:mm').format(date);
It gives this error The instance member 'date' can't be accessed in an initializer.
It represent to milliseconds, you need to multiple it with 1000 like below :
final DateTime timeStamp = DateTime.fromMillisecondsSinceEpoch(1633247247 * 1000);
It seems like that the time you've is 'seconds since epoch' so just multiplying by 1000 should give you the correct time.
final DateTime timeStamp = DateTime.fromMillisecondsSinceEpoch(1633247247 * 1000);
Download and Import
intl Pacakge
import 'package:intl/intl.dart';
Initialize a variable
String datetime;
Get Current date and conversion
Future<void> Datetimes() async{
setState(() {
DateTime now = DateTime.now();
String formattedDate = DateFormat('EEEE d MMM hh:mm:ss').format(now);
datetime=formattedDate;
});
}
Output
Saturday 3 oct 2:07:29
Refer this for DateandTime class for more formatting parameters
DateFormat-class
You need to use DateTime Formats. You can find a solution here:
https://stackoverflow.com/a/51579740/11604909
I'm trying to write a class, which able to parse multi-format and multi-locale strings into DateTime.
multi-format means that date might be: dd/MM/yyyy, MMM dd yyyy, ... (up to 10 formats)
multi-locale means that date might be: 29 Dec 2015, 29 Dez 2015, dice 29 2015 ... (up to 10 locales, like en, gr, it, jp )
Using the answer Using Joda Date & Time API to parse multiple formats I wrote:
val locales = List(
Locale.ENGLISH,
Locale.GERMAN,
...
)
val patterns = List(
"yyyy/MM/dd",
"yyyy-MM-dd",
"MMMM dd, yyyy",
"dd MMMM yyyy",
"dd MMM yyyy"
)
val parsers = patterns.flatMap(patt => locales.map(locale => DateTimeFormat.forPattern(patt).withLocale(locale).getParser)).toArray
val birthDateFormatter = new DateTimeFormatterBuilder().append(null, parsers).toFormatter
but it doesn't work:
birthDateFormatter.parseDateTime("29 Dec 2015") // ok
birthDateFormatter.parseDateTime("29 Dez 2015") // exception below
Invalid format: "29 Dez 2015" is malformed at "Dez 2015"
java.lang.IllegalArgumentException: Invalid format: "29 Dez 2015" is
malformed at "Dez 2015"
I found what all parsers: List[DateTimeParser] had "lost" their locales after an appending into birthDateFormatter: DateTimeFormatter. And birthDateFormatter has only one locale - en.
I can write:
val birthDateFormatter = locales.map(new DateTimeFormatterBuilder().append(null, parsers).toFormatter.withLocale(_))
and use it like:
birthDateFormatter.map(_.parseDateTime(stringDate))
but it will throw a lots of exceptions. It's terrible.
How can I parse multi-format and multi-locale strings using joda-time?
How can I do it any other way?
That was interesting to investigate. This is a test suite that helped me (in Java, but I hope you'll get the idea):
import java.util.*;
import java.util.stream.Collectors;
import org.joda.time.DateTime;
import org.joda.time.format.*;
import org.junit.Test;
import static org.assertj.core.api.Assertions.*;
public class JodaTimeLocaleTest {
#Test // fails on both assertions
public void testTwoLocales() {
List<Locale> locales = Arrays.asList(Locale.FRENCH, Locale.GERMAN);
DateTimeParser[] parsers = locales.stream()
.map(locale -> DateTimeFormat.forPattern("dd MMM yyyy").withLocale(locale).getParser())
.collect(Collectors.toList())
.toArray(new DateTimeParser[0]);
DateTimeFormatter formatter = new DateTimeFormatterBuilder().append(null, parsers).toFormatter();
DateTime dateTime1 = formatter.parseDateTime("29 déc. 2015");
DateTime dateTime2 = formatter.parseDateTime("29 Dez 2015");
assertThat(dateTime1).isEqualTo(new DateTime("2015-12-29T00:00:00"));
assertThat(dateTime2).isEqualTo(new DateTime("2015-12-29T00:00:00"));
}
#Test // passes
public void testFrench() {
DateTimeFormatter formatter = DateTimeFormat.forPattern("dd MMM yyyy").withLocale(Locale.FRENCH);
DateTime dateTime = formatter.parseDateTime("29 déc. 2015");
assertThat(dateTime).isEqualTo(new DateTime("2015-12-29T00:00:00"));
}
#Test // passes
public void testGerman() {
DateTimeFormatter formatter = DateTimeFormat.forPattern("dd MMM yyyy").withLocale(Locale.GERMAN);
DateTime dateTime = formatter.parseDateTime("29 Dez 2015");
assertThat(dateTime).isEqualTo(new DateTime("2015-12-29T00:00:00"));
}
}
First of all, your first example
birthDateFormatter.parseDateTime("29 Dec 2015")
passes only because your machine's default locale is English. If it was different, also this case would have failed. That's why I'm using French and German when running on a machine with English locale. In my case, both assertions fail.
It turns out that the locale is not stored in the parser, but in the formatter only. So when you do
DateTimeFormat.forPattern("dd MMM yyyy").withLocale(locale).getParser()
the locale is set on the formatter, but is then lost when creating the parser:
// DateTimeFormatter#withLocale:
public DateTimeFormatter withLocale(Locale locale) {
if (locale == getLocale() || (locale != null && locale.equals(getLocale()))) {
return this;
}
// Notice how locale does not affect the parser
return new DateTimeFormatter(iPrinter, iParser, locale,
iOffsetParsed, iChrono, iZone, iPivotYear, iDefaultYear);
}
Next, when you create a new formatter
new DateTimeFormatterBuilder().append(null, parsers).toFormatter()
it's created with the system's default locale (unless you override it with withLocale()). And that locale is used during parsing:
// DateTimeFormatter#parseDateTime
public DateTime parseDateTime(String text) {
InternalParser parser = requireParser();
Chronology chrono = selectChronology(null);
// Notice how the formatter's locale is used
DateTimeParserBucket bucket = new DateTimeParserBucket(0, chrono, iLocale, iPivotYear, iDefaultYear);
int newPos = parser.parseInto(bucket, text, 0);
// ... snipped
}
So it turns out that although you can have multiple parsers to support multiple formats, still only a single locale can be used per formatter instance.
Answer to question 1 (How can I parse multi-format and multi-locale strings using joda-time?):
No this is not possible the way you want, see also the good answer of #Adam Michalik. So the only way is just to write a list of multiple Joda-formatters and to try each one for a given input - possibly catching exceptions. You have already found the right workaround so I don't describe the details here.
Answer to question 2 (How can I do it any other way?):
My library Time4J has got a new MultiFormatParser-class since v4.11. However, I discovered some performance issues with its format engine in general (mainly due to autoboxing feature of Java) so I decided to wait with this answer until release v4.12 where I have improved the performance. According to my first benchmarks Time4J-4.12 seems to be quicker than Joda-Time (v2.9.1) because internal exceptions are strongly reduced. So I think you can give that latest version of Time4J a try and report then some feedback if it works for you.
private static final MultiFormatParser<PlainDate> TIME4J;
static {
ChronoFormatter<PlainDate> f1 =
ChronoFormatter.ofDatePattern("dd.MM.uuuu", PatternType.CLDR, Locale.ROOT);
ChronoFormatter<PlainDate> f2 =
ChronoFormatter.ofDatePattern("MM/dd/uuuu", PatternType.CLDR, Locale.ROOT);
ChronoFormatter<PlainDate> f3 =
ChronoFormatter.ofDatePattern("uuuu-MM-dd", PatternType.CLDR, Locale.ROOT);
ChronoFormatter<PlainDate> f4 =
ChronoFormatter.ofDatePattern("uuuuMMdd", PatternType.CLDR, Locale.ROOT);
ChronoFormatter<PlainDate> f5 =
ChronoFormatter.ofDatePattern("d. MMMM uuuu", PatternType.CLDR, Locale.GERMAN);
ChronoFormatter<PlainDate> f6 =
ChronoFormatter.ofDatePattern("d. MMMM uuuu", PatternType.CLDR, Locale.FRENCH);
ChronoFormatter<PlainDate> f7 =
ChronoFormatter.ofDatePattern("MMMM d, uuuu", PatternType.CLDR, Locale.US);
TIME4J = MultiFormatParser.of(f1, f2, f3, f4, f5, f6, f7);
}
...
static List<PlainDate> parse(List<String> input) {
ParseLog plog = new ParseLog();
int n = input.size();
List<PlainDate> result = new ArrayList<>(n);
for (int i = 0; i < n; i++){
String s = input.get(i);
plog.reset();
PlainDate date = TIME4J.parse(s, plog);
if (!plog.isError()) {
result.add(date);
} else {
// log or report error
}
}
return result;
}
Every single parser within MultiFormatParser keeps its own locale.
The order of parser components matters in terms of performance. Prefer those patterns and locales for first positions which are most common in your input.
I strongly recommend to use a static constant for the MultiFormatParser because a) it is immutable and b) constructing formatters is expensive in every library (and Time4J is no exception about this detail).
For interoperability with Joda-Time you can consider this conversion: LocalDate joda = new LocalDate(plainDate.getYear(), plainDate.getMonth(), plainDate.getDayOfMonth()); But keep in mind that every conversion has some extra costs. On the other side, Joda-Time offers less features than Time4J so latter one can do the full job of all date-time-zone relevant tasks, too.
I am not a scala guy but assume that following scala code might compile:
val parser = MultiFormatParser.of(patterns.flatMap(patt => locales.map(locale => ChronoFormatter.ofDatePattern(patt, PatternType.CLDR, locale))).toArray)
By the way: The performance of Joda-Time is not so bad since it was a tough task for me to make it better in Time4J-v4.12. Parsing so different patterns and locales is always a complex task. Surprising for me: The new time library built in Java-8 (package java.time) is the worst in terms of performance according to my own experiments (obviously due to internal exception handling).
If you don't work on Java-8-platforms then you can use Time4J-v3.15 (backport to Java-6-platforms).
This question is similar to How to parse ZonedDateTime with default zone? but addinitional condition.
I have a string param that represent a date in UK format: "3/6/09". It doesn't contain time, only date. But may contain it and even time zone.
And I want to parse it to ZonedDateTime.
public static ZonedDateTime parse(String value) {
DateTimeFormatter formatter = DateTimeFormatter.ofLocalizedDateTime(SHORT).withLocale(Locale.UK).withZone(ZoneId.systemDefault());
TemporalAccessor temporalAccessor = formatter.parseBest(value, ZonedDateTime::from, LocalDateTime::from, LocalDate::from);
if (temporalAccessor instanceof ZonedDateTime) {
return ((ZonedDateTime) temporalAccessor);
}
if (temporalAccessor instanceof LocalDateTime) {
return ((LocalDateTime) temporalAccessor).atZone(ZoneId.systemDefault());
}
return ((LocalDate) temporalAccessor).atStartOfDay(ZoneId.systemDefault());
}
But, it fails with exception:
java.time.format.DateTimeParseException: Text '3/6/2009' could not be parsed at index 6
It's a bug for me, or isn't?
In my opinion is not a bug. Your approach is flawed.
First of all you are returning a ZonedDateTime so it is expected that the String contains full date, time and zone information. The string "3/6/09" should be parsed to a LocalDate.
Second, you are delegating a runtime detection of format to the library. Again, you should be parsing/formatting an expected format. Your application should know wether is expecting a full date & time or a partial (only date or only time).
Anyway you will have more luck detecting the format and then using different parsing methods.
Only local date:
DateTimeFormatter
.ofLocalizedDate(FormatStyle.SHORT)
.parse(value, LocalDate::from)`
Zoned date and time:
DateTimeFormatter
.ofLocalizedDateTime(FormatStyle.SHORT, FormatStyle.SHORT)
.parse(value, ZonedDateTime::from)`
The format used can be seen using the getLocalizedDateTimePattern() method:
String fmt = DateTimeFormatterBuilder.getLocalizedDateTimePattern(
FormatStyle.SHORT, FormatStyle.SHORT, IsoChronology.INSTANCE, Locale.UK);
The result is "dd/MM/yy HH:mm".
As such, the format is expecting both a date and a time with a space separator, so that is what must be provided.
In addition, the format/parse expects there to be two digits for the day-of-month and two digits for the month-of-year. Thus, you would need to pass in "03/06/09 00:00" in order to get the result you expect, in which case you can parse directly to a LocalDateTime.
Alternatively, use ofLocalizedDate():
DateTimeFormatter formatter =
DateTimeFormatter.ofLocalizedDate(FormatStyle.SHORT).withLocale(Locale.UK);
LocalDate date = LocalDate.parse("03/06/99", formatter);
Note that the input must still have two digits for the day and month.
Alternatively, parse using a specific pattern that can handle the missing leading zeroes:
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("d/M/yy");
LocalDate date = LocalDate.parse("3/6/99", formatter);
LocalDate date = LocalDate.parse("03/06/99", formatter);
// handles both "3/6/99" and "03/06/99"
Update: Lenient parsing also handles this case:
DateTimeFormatter formatter = new DateTimeFormatterBuilder()
.parseLenient().appendPattern("dd/MM/yy").toFormatter();
LocalDate date = LocalDate.parse("3/6/99", formatter);
LocalDate date = LocalDate.parse("03/06/99", formatter);
// handles both "3/6/99" and "03/06/99"