Java Date to Google Sheets Date converter

GoogleSheetsDate.java

import java.util.Date;
import java.util.concurrent.TimeUnit;

public class GoogleSheetsDate {
    private static final long SHEETS_EPOCH_DIFFERENCE = 2209161600000L;

    static double fromJavaDate(Date date) {
        // https://stackoverflow.com/a/38015954/5525962
        long millisSinceUnixEpoch = date.getTime();
        long millisSinceSheetsEpoch = millisSinceUnixEpoch + SHEETS_EPOCH_DIFFERENCE;

        return millisSinceSheetsEpoch / (double) TimeUnit.DAYS.toMillis(1);
    }
}