I want to get the previous day (24 hours) from the current time.

e.g if current time is Date开发者_如何学运维 currentTime = new Date();

2011-04-25 12:15:31:562 GMT

How to determine time i.e

2011-04-24 12:15:31:562 GMT

You can do that using Calendar class:

Calendar cal = Calendar.getInstance();
cal.setTime ( date ); // convert your date to Calendar object
int daysToDecrement = -1;
cal.add(Calendar.DATE, daysToDecrement);
date = cal.getTime(); // again get back your date object

I would suggest you use Joda Time to start with, which is a much nicer API. Then you can use:

DateTime yesterday = new DateTime().minusDays(1);

Note that "this time yesterday" isn't always 24 hours ago though... you need to think about time zones etc. You may want to use LocalDateTime or Instant instead of DateTime.

please checkout this here: Java Date vs Calendar

Calendar cal=Calendar.getInstance();
cal.setTime(date); //not sure if date.getTime() is needed here
cal.add(Calendar.DAY_OF_MONTH, -1);
Date newDate = cal.getTime();

24 hours and 1 day are not the same thing. But you do both using Calendar:

Calendar c = Calendar.getInstance();
c.setTime(new Date());
c.add(Calendar.DATE, -1);
Date d = c.getTime();

If you are going back 24 hours, you would use Calendar.HOUR_OF_DAY

java.time

The java.util Date-Time API and their formatting API, SimpleDateFormat are outdated and error-prone. It is recommended to stop using them completely and switch to the modern Date-Time API^*.

Also, quoted below is a notice from the home page of Joda-Time:

Note that from Java SE 8 onwards, users are asked to migrate to java.time (JSR-310) - a core part of the JDK which replaces this project.

Solution using java.time, the modern Date-Time API:

import java.time.Instant;
import java.time.temporal.ChronoUnit;

public class Main {
    public static void main(String[] args) {
        Instant now = Instant.now();
        System.out.println("Now:       " + now);

        Instant yesterday = now.minus(1, ChronoUnit.DAYS);
        System.out.println("Yesterday: " + yesterday);
    }
}

Output of a sample run:

Now:       2021-07-16T20:40:24.402592Z
Yesterday: 2021-07-15T20:40:24.402592Z

ONLINE DEMO

For any reason, if you need to convert this object of Instant to an object of java.util.Date, you can do so as follows:

Date date = Date.from(odt.toInstant());

Learn more about the modern Date-Time API from Trail: Date Time.

^{* For any reason, if you have to stick to Java 6 or Java 7, you can use ThreeTen-Backport which backports most of the java.time functionality to Java 6 & 7. If you are working for an Android project and 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.}