Ask Gregorian Calendar for hour of day in java

Question

I'm using a Gregorian Calendar to set a specific date and time to an application using the set function of the Gregorian Calendar. When i use the getTime() method, it gives me the right output however when i try to access the Hour_Of_Day and Minute it gives a wrong number.

    Calendar time = new GregorianCalendar();
    time.set(2010, Calendar.JANUARY, 1, 7, 20,0);       
    hour = time.HOUR_OF_DAY;
    minute = time.MINUTE; 

The hour gives an output of 11 and the minute gives an a value of 12.
Any suggestions on how to fix this? Thanks

Answer 1

Your code is just assigning hour/minute to constants. You need to call Calendar.get(int):

hour = time.get(Calendar.HOUR_OF_DAY);
minute = time.get(Calendar.MINUTE);

Answer 2

tl;dr

myGregCal
    .toZonedDateTime()  // Convert from legacy class GregorianCalendar to modern ZonedDateTime.
    .getHour()          // Get hour-of-day, 0-23.

java.time

Much easier with the modern java.time classes that replace those troublesome old legacy date-time classes.

The ZonedDateTime class represents a moment on the timeline in a specific time zone with a resolution of nanoseconds.

Convert from your GregorianCalendar using new methods added to the old classes.

ZonedDateTime zdt = myGregCal.toZonedDateTime() ;

Or start fresh without the GregorianCalendar class.

ZoneId z = ZoneId.of( "America/Montreal" );
ZonedDateTime zdt = ZonedDateTime.of( 2010 , Month.JANUARY , 1 , 7 , 20 , 0 , 0 , z );

If you want to work with just the time-of-day portion, extract a LocalTime.

LocalTime localTime = zdt.toLocalTime() ;

If you really want the integer numbers of hours and minutes, you can interrogate for those.

int hour = zdt.getHour();
int minute = zdt.getMinute();

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About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

• Java SE 8 and SE 9 and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.