Converting ISO 8601-compliant String to epoch on KitKat

Question

I have the following ISO8601-compliant string:

2024-03-25T11:34:15.000Z

I need to convert it to java Date. I found the following solution:

Date date = Date.from(Instant.parse("2024-03-25T11:34:15.000Z"));
long epoch = date.getTime()); 

However, this requires at least Android Oreo. I need a converter that works down to KitKat. Any idea?

Tried following solutions but had the same issue:

1. Converting ISO 8601-compliant String to ZonedDateTime
2. Converting string to date using java8

I also found a solution by using JAXB but I read somewhere that it bloats my APK by 9MB! With it, the solution could be this simple:

javax.xml.bind.DatatypeConverter.parseDateTime(iso8601Date).getTimeInMillis();

Lamkin

Why not Instant.parse("2024-03-25T11:34:15.000Z").toEpochMilli()? – Philologian

Because Instant.parse() requires Android Oreo as well. – Lamkin

Well java.time exists because those old classes are buggy. You might like to investigate whether Joda can do it for you – Philologian

Your existing code -- and code using java.time in general -- will work on older Android versions when you use desugaring (or if for some reason you don’t want that, there’s also ThreeTen Android Backport). – Armagh

Don’t use Date. In your example code it’s a needless detour. Use just Instant.parse("2024-03-25T11:34:15.000Z").toEpochMillis() to get the milliseconds since the epoch. – Armagh

Does this answer your question? Convert String Date to Date in Android (Java/Kotlin) without having to deal with Call requires API level 26 – Armagh

Answer 1

This solved my issue.

private long convertDateToLong(@NonNull String iso8601Date) {
    long epoch = -1;
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSZ", Locale.US);
    try {
        Date date = sdf.parse(iso8601Date);
        if(date != null)
            epoch = date.getTime();
    } catch (ParseException e) {
        e.printStackTrace();
    }
    return epoch;
}

Lamkin

On my desktop Java 19 it fails with java.text.ParseException: Unparseable date: "2024-03-25T11:34:15.000Z". – Armagh

In my code, i think i may have used yyyy-MM-dd'T'HH:mm:ss.SSS'Z' instead of yyyy-MM-dd'T'HH:mm:ss.SSSZ. Can't check right now. – Lamkin

Never hardcode Z as a literal in your format pattern string. It’s an offset of 0 from UTC and needs to be parsed as an offset, or you will get an incorrect time. I wouldn’t rule out, though, that in the Android version format Z accepts offset 'Z` just to add to the already great confusion caused by the outdated SimpleDateFormat class. – Armagh

You're right. I will ask my web endpoint developers to fix this date that they provide to my app. And will update this question and my answer. I feel like it is my responsibility to clarify this question to not mislead other developers. – Lamkin