build.gradle

apply plugin: 'java'

repositories {
    mavenCentral()
}

dependencies {
    compile 'joda-time:joda-time:2.9.2'
}

sourceSets {
    main {
        java {
            srcDir '.'
        }
    }
}

test {
    testLogging {
        events 'passed', 'skipped', 'failed', 'standardOut', 'standardError'
    }
}

task run(type:JavaExec) {
    main = project.hasProperty('main') ? project.getProperty('main') : 'ConvertLocalUTC'
    classpath = sourceSets.main.runtimeClasspath
}

ConvertLocalUTC.java

import java.time.Instant;
import java.time.OffsetDateTime;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import org.joda.time.DateTimeZone;

public class ConvertLocalUTC {
    public static void main(final String[] args) {
        convertUTCToLocal();
        convertLocalToUTC();
    }

    private static void convertUTCToLocal() {
        System.out.println("convertUTCToLocal:");

        final long epoch = 1586754665L;
        final String sessionTimeZone = "America/Los_Angeles";

        final DateTimeZone jodaZone = DateTimeZone.forID(sessionTimeZone);
        final ZoneId javaZone = ZoneId.of(sessionTimeZone);

        System.out.println("Orig: " + epoch);

        final long reconvertedJoda = jodaZone.convertUTCToLocal(epoch * 1000L) / 1000L;
        System.out.println("Joda: " + reconvertedJoda);

        final long reconvertedJava = ZonedDateTime.ofInstant(Instant.ofEpochSecond(epoch), javaZone)
                .withZoneSameLocal(ZoneOffset.UTC).toEpochSecond();
        System.out.println("Java: " + reconvertedJava);

        System.out.println(reconvertedJoda == reconvertedJava);
    }

    private static void convertLocalToUTC() {
        System.out.println("convertLocalToUTC:");

        final long epoch = 1586754665L;
        final String sessionTimeZone = "America/Los_Angeles";

        final DateTimeZone jodaZone = DateTimeZone.forID(sessionTimeZone);
        final ZoneId javaZone = ZoneId.of(sessionTimeZone);

        System.out.println("Orig: " + epoch);

        final long reconvertedJoda = jodaZone.convertLocalToUTC(epoch * 1000L, false) / 1000L;
        System.out.println("Joda: " + reconvertedJoda);

        final long reconvertedJava = ZonedDateTime.ofInstant(Instant.ofEpochSecond(epoch), ZoneOffset.UTC)
                .withZoneSameLocal(javaZone).toEpochSecond();
        System.out.println("Java: " + reconvertedJava);

        System.out.println(reconvertedJoda == reconvertedJava);
    }
}

convertUTCToLocal:
Orig: 1586754665
Joda: 1586729465
Java: 1586729465
true
convertLocalToUTC:
Orig: 1586754665
Joda: 1586779865
Java: 1586779865
true