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I need to count back 90 days, 120 days and 160 days for a few items. How would I code this? I keep finding java code but that brings up errors when I am developing for android.

I need to take todays date and subtract the x amount of days and have it result be displayed on the screen nothing else. Thanks

Chris Odg
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    Can you be more specific about the errors and the code that produced them? – ObscureRobot Jan 04 '12 at 14:22
  • possible duplicate of [How to subtract X days from a date using Java calendar?](http://stackoverflow.com/questions/212321/how-to-subtract-x-days-from-a-date-using-java-calendar) – Basil Bourque May 27 '15 at 07:08

4 Answers4

35

You should use the Calendar class :

//Calendar set to the current date 
Calendar calendar=Calendar.getInstance();
//rollback 90 days
calendar.add(Calendar.DAY_OF_YEAR, -90);
//now the date is 90 days back
Log.i("MyApp","90 days ago:"+calendar.getTime().toString());
Ovidiu Latcu
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  • roll() is adding to fields, not substracting. But it is not correct, because it does not change larger fields. See http://docs.oracle.com/javase/1.4.2/docs/api/java/util/Calendar.html – nagylzs Nov 08 '12 at 12:38
11

Use the Calendar object...

Calendar calendar = Calendar.getInstance();
calendar.add(Calendar.DATE, -90); //etc
Damian
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3

tl;dr

LocalDate.now( ZoneId.of( "America/Montreal" ) )
         .minusDays( 90 )

java.time

Other answers here are outdated. The modern way is with java.time classes.

LocalDate

The LocalDate class represents a date-only value without time-of-day and without time zone.

A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.

ZoneId z = ZoneId.of( "America/Montreal" ) ;
LocalDate today = LocalDate.now( z ) ;

You can then add or subtract days.

LocalDate ago090 = today.minusDays( 90 ) ;
LocalDate ago120 = today.minusDays( 120 ) ;
LocalDate ago160 = today.minusDays( 160 ) ;

To generate a string in standard ISO 8601 format of YYYY-MM-DD, call toString. For other formats, search Stack Overflow for DateTimeFormatter class to see many examples and discussions.

String output = ago120.toString() ;

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 java.time.

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 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.

Community
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Basil Bourque
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0

You should be able to use the Calendar class to achieve what you want: http://docs.oracle.com/javase/1.4.2/docs/api/java/util/Calendar.html.

You can then call on your calendar object with the current date .add(Calendar.DAY_OF_YEAR, -90); and so on.

jcxavier
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