Various quarter-related DateTime functions in C#

The DateTime object – or struct – lacks functions for quarters. You can e.g. add minutes, months, days etc. to a date but not quarters.

Here comes a short list of simple quarter-related functions.

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Truncate a DateTime in C#

Occasionally you need to truncate a date to the nearest year, month, day etc. E.g. you need to transform the date 2015-06-05 15:33:30 into 2015-06-05 00:00:00, i.e. truncate it to the nearest day and set the lower levels of the date to 0.

Here comes a series of extension methods to help you with that:

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Converting a string into a DateTime with an exact date format in C# .NET

How do you read the date “03-10-2014”? For some of you this will be October 03 2014. For others, especially those from the US this will be interpreted as March 10 2014. This is because dates are represented in different formats in different cultures.

Consider the following code:

string dateString = "03-10-2014";
DateTime parsedDate = DateTime.Parse(dateString);
string toString = parsedDate.ToLongDateString();

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Localising dates in Java 8 using DateTimeFormatter

Introduction

In this post we saw how to format dates according to some ISO and RCF standards. They can help you to quickly format a date in a standardised way. However, if you’re looking for date localisation then you’ll need something else.

By localising dates we mean that we want to show dates in an application according to the user’s region. A Japanese user will want to see the dates according to the Japanese date convention. You can store UTC dates internally according to an ISO standard but follow some local convention when presenting it on the screen.

Locales

A Locale represents a region and one or more corresponding cultures, most often with a country and one or more languages. You can easily list all available Locales:

Locale[] locales = Locale.getAvailableLocales();
        for (Locale locale : locales)
        {
            System.out.println(locale.getCountry());
            System.out.println(locale.getDisplayCountry());
            System.out.println(locale.getDisplayLanguage());
        }

You’ll see values such as…

PE
Peru
Spanish
ID
Indonesia
Indonesian
GB
United Kingdom
English

Some locales are stored as static properties of the Locale object, e.g.:

Locale.JAPAN
Locale.FRANCE
Locale.US

We’ll need to use the ZonedDateTime object to format a date according to a Locale. The following code will format the UTC date according to the US standard:

ZonedDateTime utcDateZoned = ZonedDateTime.now(ZoneId.of("Etc/UTC"));
DateTimeFormatter pattern = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL).withLocale(Locale.US);
System.out.println(utcDateZoned.format(pattern));

The output will be Friday, November 21, 2014 1:45:14 PM UTC.

Let’s see the UTC dates in France and Japan:

DateTimeFormatter pattern = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL).withLocale(Locale.FRANCE);
System.out.println(utcDateZoned.format(pattern));

… vendredi 21 novembre 2014 13 h 50 UTC

DateTimeFormatter pattern = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.FULL).withLocale(Locale.JAPAN);
System.out.println(utcDateZoned.format(pattern));

2014年11月21日 13時51分34秒 UTC

View all posts related to Java here.

Formatting dates in Java 8 using DateTimeFormatter

Introduction

Formatting dates – and numbers for that matter – can be a complex matter. The DateTimeFormatter class provides pre-defined formats that adhere to ISO and RCF specifications.

DateTimeFormatter

The following date related classes we’ve seen on this blog, i.e.

…have a method called “format” which accepts a DateTimeFormatter class. This class has a number of pre-defined formats that you can readily use in your application. Note that not all such formats will be available. The availability depends on the exact object type of the date class. E.g. ISO_ZONED_DATE_TIME won’t work with LocalDateTime as it is meant to format zoned dates. Also, ISO_DATE_TIME won’t be available for the LocalDate class as it has no concept of time units below the level of days.

Let’s test all the predefined values with the above date types.

LocalDate

We run the following code and check the output:

System.out.println("Running example with LocalDate class.");
LocalDate now = LocalDate.now();
        try
        {
            System.out.println("ISO_DATE: " + now.format(DateTimeFormatter.ISO_DATE));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_DATE is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("BASIC_ISO_DATE: " + now.format(DateTimeFormatter.BASIC_ISO_DATE));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("BASIC_ISO_DATE is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_DATE_TIME: " + now.format(DateTimeFormatter.ISO_DATE_TIME));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_DATE_TIME is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_INSTANT: " + now.format(DateTimeFormatter.ISO_INSTANT));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_INSTANT is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_LOCAL_DATE: " + now.format(DateTimeFormatter.ISO_LOCAL_DATE));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_LOCAL_DATE is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_LOCAL_DATE_TIME: " + now.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_LOCAL_DATE_TIME is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_LOCAL_TIME: " + now.format(DateTimeFormatter.ISO_LOCAL_TIME));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_LOCAL_TIME is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_OFFSET_DATE: " + now.format(DateTimeFormatter.ISO_OFFSET_DATE));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_OFFSET_DATE is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_OFFSET_DATE_TIME: " + now.format(DateTimeFormatter.ISO_OFFSET_DATE_TIME));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_OFFSET_DATE_TIME is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_OFFSET_TIME: " + now.format(DateTimeFormatter.ISO_OFFSET_TIME));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_OFFSET_TIME is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_ORDINAL_DATE: " + now.format(DateTimeFormatter.ISO_ORDINAL_DATE));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_ORDINAL_DATE is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_TIME: " + now.format(DateTimeFormatter.ISO_TIME));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_TIME is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_WEEK_DATE: " + now.format(DateTimeFormatter.ISO_WEEK_DATE));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_WEEK_DATE is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("ISO_ZONED_DATE_TIME: " + now.format(DateTimeFormatter.ISO_ZONED_DATE_TIME));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("ISO_ZONED_DATE_TIME is not supported: " + e.getMessage());
        }
        try
        {
            System.out.println("RFC_1123_DATE_TIME: " + now.format(DateTimeFormatter.RFC_1123_DATE_TIME));
        } catch (UnsupportedTemporalTypeException e)
        {
            System.out.println("RFC_1123_DATE_TIME is not supported: " + e.getMessage());
        }

We get the following output:

Running example with LocalDate class.
ISO_DATE: 2014-11-01
BASIC_ISO_DATE: 20141101
ISO_DATE_TIME is not supported: Unsupported field: HourOfDay
ISO_INSTANT is not supported: Unsupported field: InstantSeconds
ISO_LOCAL_DATE: 2014-11-01
ISO_LOCAL_DATE_TIME is not supported: Unsupported field: HourOfDay
ISO_LOCAL_TIME is not supported: Unsupported field: HourOfDay
ISO_OFFSET_DATE is not supported: Unsupported field: OffsetSeconds
ISO_OFFSET_DATE_TIME is not supported: Unsupported field: HourOfDay
ISO_OFFSET_TIME is not supported: Unsupported field: HourOfDay
ISO_ORDINAL_DATE: 2014-305
ISO_TIME is not supported: Unsupported field: HourOfDay
ISO_WEEK_DATE: 2014-W44-6
ISO_ZONED_DATE_TIME is not supported: Unsupported field: HourOfDay
RFC_1123_DATE_TIME is not supported: Unsupported field: HourOfDay

LocalTime

We run the same code as above but change the class type:

System.out.println("Running example with LocalTime class.");
LocalTime now = LocalTime.now();

…and here’s the output, again with Locale set to Sweden:

Running example with LocalTime class.
ISO_DATE is not supported: Unsupported field: Year
BASIC_ISO_DATE is not supported: Unsupported field: Year
ISO_DATE_TIME is not supported: Unsupported field: Year
ISO_INSTANT is not supported: Unsupported field: InstantSeconds
ISO_LOCAL_DATE is not supported: Unsupported field: Year
ISO_LOCAL_DATE_TIME is not supported: Unsupported field: Year
ISO_LOCAL_TIME: 22:02:52.932
ISO_OFFSET_DATE is not supported: Unsupported field: Year
ISO_OFFSET_DATE_TIME is not supported: Unsupported field: Year
ISO_OFFSET_TIME is not supported: Unsupported field: OffsetSeconds
ISO_ORDINAL_DATE is not supported: Unsupported field: Year
ISO_TIME: 22:02:52.932
ISO_WEEK_DATE is not supported: Unsupported field: WeekBasedYear
ISO_ZONED_DATE_TIME is not supported: Unsupported field: Year
RFC_1123_DATE_TIME is not supported: Unsupported field: DayOfMonth

Most formats are not supported by LocalTime as there’s no notion of days, months etc. in that object.

LocalDateTime

Run the same code with “now” set as follows:

System.out.println("Running example with LocalDateTime class.");
LocalDateTime now = LocalDateTime.now();

…and I got the following output:

Running example with LocalTime class.
ISO_DATE: 2014-11-01
BASIC_ISO_DATE: 20141101
ISO_DATE_TIME: 2014-11-01T22:07:24.329
ISO_INSTANT is not supported: Unsupported field: InstantSeconds
ISO_LOCAL_DATE: 2014-11-01
ISO_LOCAL_DATE_TIME: 2014-11-01T22:07:24.329
ISO_LOCAL_TIME: 22:07:24.329
ISO_OFFSET_DATE is not supported: Unsupported field: OffsetSeconds
ISO_OFFSET_DATE_TIME is not supported: Unsupported field: OffsetSeconds
ISO_OFFSET_TIME is not supported: Unsupported field: OffsetSeconds
ISO_ORDINAL_DATE: 2014-305
ISO_TIME: 22:07:24.329
ISO_WEEK_DATE: 2014-W44-6
ISO_ZONED_DATE_TIME is not supported: Unsupported field: OffsetSeconds
RFC_1123_DATE_TIME is not supported: Unsupported field: OffsetSeconds

ZonedDateTime

This is probably the most interesting case as it supports all the predefined formats in DateTimeFormatter. Let’s look at an example with Australia/Adelaide:

System.out.println("Running example with ZonedDateTime class.");
ZoneId brisbane = ZoneId.of("Australia/Adelaide");
ZonedDateTime now = ZonedDateTime.of(LocalDateTime.now(), brisbane);

Running example with ZonedDateTime class.
ISO_DATE: 2014-11-01+10:30
BASIC_ISO_DATE: 20141101+1030
ISO_DATE_TIME: 2014-11-01T22:13:48.87+10:30[Australia/Adelaide]
ISO_INSTANT: 2014-11-01T11:43:48.870Z
ISO_LOCAL_DATE: 2014-11-01
ISO_LOCAL_DATE_TIME: 2014-11-01T22:13:48.87
ISO_LOCAL_TIME: 22:13:48.87
ISO_OFFSET_DATE: 2014-11-01+10:30
ISO_OFFSET_DATE_TIME: 2014-11-01T22:13:48.87+10:30
ISO_OFFSET_TIME: 22:13:48.87+10:30
ISO_ORDINAL_DATE: 2014-305+10:30
ISO_TIME: 22:13:48.87+10:30
ISO_WEEK_DATE: 2014-W44-6+10:30
ISO_ZONED_DATE_TIME: 2014-11-01T22:13:48.87+10:30[Australia/Adelaide]
RFC_1123_DATE_TIME: Sat, 1 Nov 2014 22:13:48 +1030

So you see that these predefined formatters follow the accepted ISO and RFC specifications and won’t actually show the localised date format the way dates are formatted in e.g. Japan or the US.

We’ll take a look at date localisation using the DateTimeFormatter in the next post in this series.

View all posts related to Java here.

Time zones in Java 8 Date and Time API

Introduction

I know for a fact that all programmers love working with time zones. Chances are high that you, as a reader of this blog, are also a programmer so I bet you also just love time zones. Let’s see what Java 8 offers as far as time zones are concerned.

Time zones

So far in this series on the date and time in Java 8 we always worked with the local time zone found on your computer. All date-related classes, such as LocalTime or LocalDateTime allow you to easily set the time zone. Here’s an example with the LocalDateTime class:

ZoneId zoneId = ZoneId.of("Europe/Budapest");
LocalDateTime now = LocalDateTime.now(zoneId);

Where are these string values coming from? They follow what Internet Assigned Numbers Authority (IANA) has in its database. That page doesn’t offer a readable list of time zones, they are only available in compressed .tar.gz files. In case you don’t want to deal with those you can find the time zones on Wikipedia.

You can get the full list of time zones in Java 8 as follows:

Set<String> availableZoneIds = ZoneId.getAvailableZoneIds();

There’s support for 586 time zones which should be enough for all cases.

You can view the default time zone of your environment like this:

ZoneId systemDefault = ZoneId.systemDefault();

…which in my case returned “Europe/Berlin”.

Setting the time zone will also take care of the summer and winter time adjustments automatically.

ZonedDateTime

What if you want to set the parts of the date individually and set the time zone at the same time? We need to turn to the ZonedDateTime class. The static “of” method has many overloads for granular access. Here’s an example that takes a LocalDateTime instance and a ZoneId, we convert the Budapest time to the Brisbane time zone:

ZoneId zoneId = ZoneId.of("Europe/Budapest");
LocalDateTime now = LocalDateTime.now(zoneId);
ZoneId brisbane = ZoneId.of("Australia/Adelaide");
ZonedDateTime zonedDate = ZonedDateTime.of(now, brisbane);

Here’s another example that builds a zoned time out of LocalDate and LocalTime:

ZoneId canadaTz = ZoneId.of("Canada/Central");
LocalDate canadaDate = LocalDate.of(2014, Month.MARCH, 15);
LocalTime canadaTime = LocalTime.of(13, 24, 12);
ZonedDateTime canadaZonedTime = ZonedDateTime.of(canadaDate, canadaTime, canadaTz);

The ZonedDateTime class behaves in much the same way as LocalDateTime and has very similar methods, like “plus”, “minus”, “get” etc. I won’t repeat them here, you can check out the following posts to see how they behave:

You can find the difference in minutes between two zoned times as follows:

ZoneId canadaTz = ZoneId.of("Canada/Central");
LocalDate canadaDate = LocalDate.of(2014, Month.MARCH, 15);
LocalTime canadaTime = LocalTime.of(13, 24, 12);
ZonedDateTime canadaZonedTime = ZonedDateTime.of(canadaDate, canadaTime, canadaTz);
        
ZoneId santoDomingoTz = ZoneId.of("America/Santo_Domingo");
LocalDate santoDomingoDate = LocalDate.of(2014, Month.MARCH, 15);
LocalTime santoDomingoTime = LocalTime.of(13, 24, 12);
ZonedDateTime santoDomingoZonedTime = ZonedDateTime.of(santoDomingoDate, santoDomingoTime, santoDomingoTz);
        
long until = santoDomingoZonedTime.until(canadaZonedTime, ChronoUnit.MINUTES);

“until” will be 60 minutes at the time of writing this post as Canada observes Daylight Saving Time whereas Dominica in the Caribbean region does not. “until” will be 120 minutes as soon as DST is over.

You can easily switch the time zone of a ZonedDateTime instance:

ZonedDateTime converted = santoDomingoZonedTime.withZoneSameInstant(ZoneId.systemDefault());

View the next post here which takes up formatting zoned date times.

View all posts related to Java here.

Adjusting the date in Java 8 Date and Time API

Introduction

We saw a couple of new concepts in the Java 8 Date and Time API on this blog:

All the above classes expose methods called “with” with a couple of overloads. LocalDate, LocalTime and LocalDateTime come with other methods whose names start with “with”, such as withSeconds or withMonth depending on the supported level of time unit. The “with” methods adjust some value of the date-related instances and return a new instance.

Examples

Here’s how you can adjust the day within the month of the LocalDate instance:

LocalDate currentLocalDate = LocalDate.now();
LocalDate dayOfMonthAdjusted = currentLocalDate.withDayOfMonth(12);

The above code will set the day to the 12th of the month of “currentLocalDate” and return the new LocalDate instance “dayOfMonthAdjusted”. Here come some similar adjusters:

LocalDate currentLocalDate = LocalDate.now();
LocalDate dayOfYearAdjusted = currentLocalDate.withDayOfYear(234);

I wrote this post in the year of 2014 so the year value of currentLocalDate was 2014. withDayOfYear will set the day within the year starting from Jan 01. The value of 234 will set the “dayOfYearAdjusted” to 2014-08-22.

The withMonth and withYear modify the month and year values respectively.

LocalTime has similar methods: withHour, withMinute, withSecond and withNano that behave the same way as e.g. withMonth in the case of the LocalDate class.

LocalDateTime has all those methods available: from withYear down to withNano as that class supports these levels of granularity.

TemporalAdjuster

The “with” methods of the previous section are not available for the Instant class. There’s however an interesting overload of “with” for both LocalDate and Instant, the one which accepts a TemporalAdjuster object. The following example will set find the most recent Monday relative to the current day:

LocalDate previousMonday = currentLocalDate.with(TemporalAdjusters.previous(DayOfWeek.MONDAY));

Similarly, you can find the following Monday:

LocalDate nextMonday = currentLocalDate.with(TemporalAdjusters.next(DayOfWeek.MONDAY));

The following code will find the 3rd Monday of the current month:

LocalDate thirdMonday = currentLocalDate.with(TemporalAdjusters.dayOfWeekInMonth(3, DayOfWeek.MONDAY));

TemporalAdjusters has some more interesting constants, the method names are pretty descriptive:

  • firstDayOfMonth
  • firstDayOfNextMonth
  • lastInMonth and firstInMonth which accepts a DayOfWeek enumeration, i.e. you can find the first/last Monday, Tuesday etc. of a given month
  • lastDayOfMonth

Read the next part on Java 8 Dates here.

View all posts related to Java here.

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