how do I compare time part from Date in java

Question

I need to compare the time part from 2 date/time variables to see if the time is inbetween the current time in android. How can I do that?

    Boolean InBetweenTime(Date currentTime, Date StartTime, Date EndTime)
{
    Boolean result = false;
    Calendar calendar = Calendar.getInstance();
    if ((!currentTime.before(StartTime))&&(!currentTime.after(EndTime))){
        //between time
    } else {
        //not inbetween time
    }
    return result;
}

Answer 1

If what you need is to compare only time, ignoring date, then you should do something like this, so your 'date' part be equal in all three variables.

Boolean InBetweenTime(Date currentTime, Date startTime, Date endTime){
    Boolean result = false;

    //calendar for currentTime
    Calendar currentCal = Calendar.getInstance();
    currentCal.setTime(currentTime);
    //calendar for startTime
    Calendar startCal = Calendar.getInstance();
    startCal.setTime(startTime);
    //calendar for endTime
    Calendar endCal = Calendar.getInstance();
    endCal.setTime(endTime);
    //set corresponding date fields of startTime and endTime to be equal t ocurrentTime, so you compare only time fields
    startCal.set(currentCal.get(Calendar.YEAR), currentCal.get(Calendar.MONTH), currentCal.get(Calendar.DAY_OF_MONTH));
    endCal.set(currentCal.get(Calendar.YEAR), currentCal.get(Calendar.MONTH), currentCal.get(Calendar.DAY_OF_MONTH));
    //return true if between, false otherwise
    return (!currentTime.before(startCal.getTime())) && (!currentTime.after(endCal.getTime()));
}

Answer 2

To get the time part of a Date (which is a date/time value), use this:

Date date = ...
Instant instant = d.toInstant();
Instant midnight = instant.truncatedTo(ChronoUnit.DAYS);
Duration timeSinceMidnight = Duration.between(midnight, instant);
System.out.println(timeSinceMidnight);

Answer 3

Solution using java.time API (Java 8+)

The solution would be clean and clear using the modern date-time API.

Demo:

import java.time.Instant;
import java.time.LocalTime;
import java.time.ZoneId;

public class Main {
    public static void main(String[] args) {
        // Tests
        System.out.println(isBetween(Instant.parse("2022-11-20T20:30:00Z"), Instant.parse("2022-11-15T23:45:00Z")));
        System.out.println(isBetween(Instant.parse("2022-11-20T10:20:30Z"), Instant.parse("2022-11-15T20:10:05Z")));
        System.out.println(isBetween(Instant.parse("2022-11-20T10:20:30Z"), Instant.parse("2022-11-15T10:20:30Z")));
    }

    static boolean isBetween(Instant startInstant, Instant endInstant) {
        LocalTime currentTime = getTime(Instant.now());
        LocalTime startTime = getTime(startInstant);
        LocalTime endTime = getTime(endInstant);
        return currentTime.isAfter(startTime) && currentTime.isBefore(endTime);
    }

    static LocalTime getTime(Instant instant) {
        return instant.atZone(ZoneId.systemDefault()).toLocalTime();
    }
}

Output when I ran it at ~ 2022-11-30T23:32:00Z:

true
false
false

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

Solution using Java version < 8

If your project is open to using 3rd party library for date-time, I recommend you check How to use ThreeTenABP in Android Project. The ThreeTenABP library makes it possible to backport java.time API to Java 6 and 7.

If you want to stick to the standard library of Java version < 8, here is a solution:

The trick is to set today's year, month and day into the startDate and endDate and then you can compare them as usual. If you have year, month and day the same across all three instances of Date, basically you comparing just their times.

Demo:

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;

public class Main {
    public static void main(String[] args) throws ParseException {
        // Tests
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssXXX");
        sdf.setTimeZone(TimeZone.getTimeZone("UTC"));
        System.out.println(isBetween(sdf.parse("2022-11-20T20:30:00Z"), sdf.parse("2022-11-15T23:45:00Z")));
        System.out.println(isBetween(sdf.parse("2022-11-20T10:20:30Z"), sdf.parse("2022-11-15T20:10:05Z")));
        System.out.println(isBetween(sdf.parse("2022-11-20T10:20:30Z"), sdf.parse("2022-11-15T10:20:30Z")));
    }

    static boolean isBetween(Date startTime, Date endTime) {
        Date currentTime = new Date();
        // System.out.println(currentTime);
        Calendar currentCal = Calendar.getInstance();
        currentCal.setTime(currentTime);
        int year = currentCal.get(Calendar.YEAR);
        int month = currentCal.get(Calendar.MONTH);
        int day = currentCal.get(Calendar.DAY_OF_MONTH);

        // Set today's year, month and day into the startDate
        Calendar startCal = Calendar.getInstance();
        startCal.setTime(startTime);
        startCal.set(year, month, day);
        startTime = startCal.getTime();
        // System.out.println(startTime);

        // Set today's year, month and day into the endDate
        Calendar endCal = Calendar.getInstance();
        endCal.setTime(endTime);
        endCal.set(year, month, day);
        endTime = endCal.getTime();
        // System.out.println(endTime);

        return currentTime.after(startTime) && currentTime.before(endTime);
    }
}

Output when I ran it at ~ 2022-11-30T23:33:00Z:

true
false
false