How to get the current date/time in Java
It depends on what form of date / time you want:
If you want the date / time as a single numeric value, then
System.currentTimeMillis()
gives you that, expressed as the number of milliseconds after the UNIX epoch (as a Javalong
). This value is a delta from a UTC time-point, and is independent of the local time-zone1.If you want the date / time in a form that allows you to access the components (year, month, etc) numerically, you could use one of the following:
new Date()
gives you aDate
object initialized with the current date / time. The problem is that theDate
API methods are mostly flawed ... and deprecated.Calendar.getInstance()
gives you aCalendar
object initialized with the current date / time, using the defaultLocale
andTimeZone
. Other overloads allow you to use a specificLocale
and/orTimeZone
. Calendar works ... but the APIs are still cumbersome.new org.joda.time.DateTime()
gives you a Joda-time object initialized with the current date / time, using the default time zone and chronology. There are lots of other Joda alternatives ... too many to describe here. (But note that some people report that Joda time has performance issues.; e.g. https://stackoverflow.com/questions/6280829.)in Java 8, calling
java.time.LocalDateTime.now()
andjava.time.ZonedDateTime.now()
will give you representations2 for the current date / time.
Prior to Java 8, most people who know about these things recommended Joda-time as having (by far) the best Java APIs for doing things involving time point and duration calculations.
With Java 8 and later, the standard java.time
package is recommended. Joda time is now considered "obsolete", and the Joda maintainers are recommending that people migrate.3.
1 - System.currentTimeMillis()
gives the "system" time. While it is normal practice for the system clock to be set to (nominal) UTC, there will be a difference (a delta) between the local UTC clock and true UTC. The size of the delta depends on how well (and how often) the system's clock is synced with UTC.
2 - Note that LocalDateTime doesn't include a time zone. As the javadoc says: "It cannot represent an instant on the time-line without additional information such as an offset or time-zone."
3 - Note: your Java 8 code won't break if you don't migrate, but the Joda codebase may eventually stop getting bug fixes and other patches. As of 2020-02, an official "end of life" for Joda has not been announced, and the Joda APIs have not been marked as Deprecated.
How to get the current date and time of your timezone in Java?
Date
is always UTC-based... or time-zone neutral, depending on how you want to view it. A Date
only represents a point in time; it is independent of time zone, just a number of milliseconds since the Unix epoch. There's no notion of a "local instance of Date
." Use Date
in conjunction with Calendar
and/or TimeZone.getDefault()
to use a "local" time zone. Use TimeZone.getTimeZone("Europe/Madrid")
to get the Madrid time zone.
... or use Joda Time, which tends to make the whole thing clearer, IMO. In Joda Time you'd use a DateTime
value, which is an instant in time in a particular calendar system and time zone.
In Java 8 you'd use java.time.ZonedDateTime
, which is the Java 8 equivalent of Joda Time's DateTime
.
How can I get the current date and time in UTC or GMT in Java?
java.util.Date
has no specific time zone, although its value is most commonly thought of in relation to UTC. What makes you think it's in local time?
To be precise: the value within a java.util.Date
is the number of milliseconds since the Unix epoch, which occurred at midnight January 1st 1970, UTC. The same epoch could also be described in other time zones, but the traditional description is in terms of UTC. As it's a number of milliseconds since a fixed epoch, the value within java.util.Date
is the same around the world at any particular instant, regardless of local time zone.
I suspect the problem is that you're displaying it via an instance of Calendar which uses the local timezone, or possibly using Date.toString()
which also uses the local timezone, or a SimpleDateFormat
instance, which, by default, also uses local timezone.
If this isn't the problem, please post some sample code.
I would, however, recommend that you use Joda-Time anyway, which offers a much clearer API.
How to set time zone of a java.util.Date?
Use DateFormat. For example,
SimpleDateFormat isoFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss");
isoFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
Date date = isoFormat.parse("2010-05-23T09:01:02");
SimpleDateFormat shows wrong local Time
Use Europe/Berlin
instead of CEST
and you will get the expected result.
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
public class Main {
public static void main(String[] args) {
SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z");
sdf2.setTimeZone(TimeZone.getTimeZone("Europe/Berlin"));
System.out.println(sdf2.format(new Date()));
}
}
Output:
2020-09-27 18:38:04 +0200
A piece of advice:
I recommend you switch from the outdated and error-prone java.util
date-time API and SimpleDateFormat
to the modern java.time
date-time API and the corresponding formatting API (package, java.time.format
). Learn more about the modern date-time API from Trail: Date Time. If your Android API level is still not compliant with Java-8, check Java 8+ APIs available through desugaring and How to use ThreeTenABP in Android Project.
Using the modern date-time API:
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
public class Main {
public static void main(String[] args) {
ZonedDateTime zdt = ZonedDateTime.now(ZoneId.of("Europe/Berlin"));
// Default format
System.out.println(zdt);
// Some custom format
System.out.println(zdt.format(DateTimeFormatter.ofPattern("EEEE dd uuuu hh:mm:ss a z")));
}
}
Output:
2020-09-27T18:42:53.620168+02:00[Europe/Berlin]
Sunday 27 2020 06:42:53 pm CEST
The modern API will alert you whereas legacy API may failover:
import java.time.ZoneId;
import java.time.ZonedDateTime;
public class Main {
public static void main(String[] args) {
ZonedDateTime zdt = ZonedDateTime.now(ZoneId.of("CEST"));
// ...
}
}
Output:
Exception in thread "main" java.time.zone.ZoneRulesException: Unknown time-zone ID: CEST
at java.base/java.time.zone.ZoneRulesProvider.getProvider(ZoneRulesProvider.java:279)
at java.base/java.time.zone.ZoneRulesProvider.getRules(ZoneRulesProvider.java:234)
at java.base/java.time.ZoneRegion.ofId(ZoneRegion.java:120)
at java.base/java.time.ZoneId.of(ZoneId.java:408)
at java.base/java.time.ZoneId.of(ZoneId.java:356)
at Main.main(Main.java:6)
As you can see, you get an exception in this case whereas SimpleDateFormat
will give you undesirable result as shown below:
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
public class Main {
public static void main(String[] args) {
SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z");
sdf2.setTimeZone(TimeZone.getTimeZone("CEST"));
System.out.println(sdf2.format(new Date()));
}
}
Output:
2020-09-27 16:47:45 +0000
You might be wondering what this undesirable result refers to. The answer is: when SimpleDateFormat
doesn't understand a time-zone, it failovers (defaults) to GMT
(same as UTC
) i.e. it has ignored CEST
and applied GMT
in this case (not a good feature IMHO ).
Check if a given time lies between two times regardless of date
You can use the Calendar
class in order to check.
For example:
try {
String string1 = "20:11:13";
Date time1 = new SimpleDateFormat("HH:mm:ss").parse(string1);
Calendar calendar1 = Calendar.getInstance();
calendar1.setTime(time1);
calendar1.add(Calendar.DATE, 1);
String string2 = "14:49:00";
Date time2 = new SimpleDateFormat("HH:mm:ss").parse(string2);
Calendar calendar2 = Calendar.getInstance();
calendar2.setTime(time2);
calendar2.add(Calendar.DATE, 1);
String someRandomTime = "01:00:00";
Date d = new SimpleDateFormat("HH:mm:ss").parse(someRandomTime);
Calendar calendar3 = Calendar.getInstance();
calendar3.setTime(d);
calendar3.add(Calendar.DATE, 1);
Date x = calendar3.getTime();
if (x.after(calendar1.getTime()) && x.before(calendar2.getTime())) {
//checkes whether the current time is between 14:49:00 and 20:11:13.
System.out.println(true);
}
} catch (ParseException e) {
e.printStackTrace();
}
See if the current time falls within a specific range of time in the current day in Java
this is all you should need to do, this method is loosely coupled from the input and highly coherent.
boolean isNowBetweenDateTime(final Date s, final Date e)
{
final Date now = new Date();
return now.after(s) && now.before(e);
}
how you get the Date objects for start and end is irrelevant to comparing them. You are making things way more complicated than you need to with passing String
representations around.
Here is a better way to get the start and end dates, again loosely coupled and highly coherent.
private Date dateFromHourMinSec(final String hhmmss)
{
if (hhmmss.matches("^[0-2][0-9]:[0-5][0-9]:[0-5][0-9]$"))
{
final String[] hms = hhmmss.split(":");
final GregorianCalendar gc = new GregorianCalendar();
gc.set(Calendar.HOUR_OF_DAY, Integer.parseInt(hms[0]));
gc.set(Calendar.MINUTE, Integer.parseInt(hms[1]));
gc.set(Calendar.SECOND, Integer.parseInt(hms[2]));
gc.set(Calendar.MILLISECOND, 0);
return gc.getTime();
}
else
{
throw new IllegalArgumentException(hhmmss + " is not a valid time, expecting HH:MM:SS format");
}
}
Now you can make two well named method calls that will be pretty self documenting.
Related Topics
How to Handle It with Scanner (Java)
A Confusion About Java String Literal Pool and String's Concatenation
Java.Net.Connectexception :Connection Timed Out: Connect
Prevent Swing Gui Locking Up During a Background Task
Filling Combobox from Database by Using Hibernate in Java
How to Quickly Determine If a Method Is Overridden in Java
Jdbc Driver Throws "Resultset Closed" Exception on Empty Resultset
Annotation to Filter Results of a @Onetomany Association
Totally Confused with Java.Exe
How to Change the Color of Titlebar in Jframe
Is Asynchronous Jdbc Call Possible
How to Change Background Color of Jtabbedpane
Constantly Update UI in Java Fx Worker Thread
Location of Hibernate.Cfg.Xml in Project