find ZonedDateTime is today, yesterday or else

Question

I have a list of ZonedDateTime objects (Eg. 2023-01-01T20:40:01.001+05:30[Asia/Kolkata])

I need to write a method to get the below results.

if ZonedDateTime is today -> return "Today"
if ZonedDateTime is yesterday -> return "Yesterday"
else -> return ZonedDateTime in "yyyy-MM-dd" format -> (Eg. DateTimeFormatter.ofPattern("yyyy-MM-dd").format(zonedDateTime))

How can I calculate if ZonedDateTime is today, tomorrow or else? "Today" as seen in the same timezone as ZonedDateTime object.

Answer 1

You don't actually need to work with ZonedDateTimes for the most part. Just find out what day today is in the desired ZoneId, and then work with LocalDates from that point onwards.

Check if toLocalDate() is equal to today, or if it is equal to today minus one day.

public static String getRelativeDateString(ZonedDateTime zdt) {
    var today = LocalDate.now(zdt.getZone());
    var ld = zdt.toLocalDate();

    if (ld.equals(today)) {
        return "Today";
    } else if (ld.equals(today.minusDays(1))) {
        return "Yesterday";
    } else {
        return ld.format(DateTimeFormatter.ISO_LOCAL_DATE /* or another formatter */);
    }
}