How can I calculate a time span in Java and format the output?

^{Since everyone shouts "YOODAA!!!" but noone posts a concrete example, here's my contribution.}

You could also do this with Joda-Time. Use Period to represent a period. To format the period in the desired human representation, use PeriodFormatter which you can build by PeriodFormatterBuilder.

Here's a kickoff example:

DateTime myBirthDate = new DateTime(1978, 3, 26, 12, 35, 0, 0);
DateTime now = new DateTime();
Period period = new Period(myBirthDate, now);

PeriodFormatter formatter = new PeriodFormatterBuilder()
    .appendYears().appendSuffix(" year, ", " years, ")
    .appendMonths().appendSuffix(" month, ", " months, ")
    .appendWeeks().appendSuffix(" week, ", " weeks, ")
    .appendDays().appendSuffix(" day, ", " days, ")
    .appendHours().appendSuffix(" hour, ", " hours, ")
    .appendMinutes().appendSuffix(" minute, ", " minutes, ")
    .appendSeconds().appendSuffix(" second", " seconds")
    .printZeroNever()
    .toFormatter();

String elapsed = formatter.print(period);
System.out.println(elapsed + " ago");

Much more clear and concise, isn't it?

This prints by now

32 years, 1 month, 1 week, 5 days, 6 hours, 56 minutes, 24 seconds ago

^{_{(Cough, old, cough)}}

    Date start = new Date(1167627600000L); // JANUARY_1_2007
    Date end = new Date(1175400000000L); // APRIL_1_2007


    long diffInSeconds = (end.getTime() - start.getTime()) / 1000;

    long diff[] = new long[] { 0, 0, 0, 0 };
    /* sec */diff[3] = (diffInSeconds >= 60 ? diffInSeconds % 60 : diffInSeconds);
    /* min */diff[2] = (diffInSeconds = (diffInSeconds / 60)) >= 60 ? diffInSeconds % 60 : diffInSeconds;
    /* hours */diff[1] = (diffInSeconds = (diffInSeconds / 60)) >= 24 ? diffInSeconds % 24 : diffInSeconds;
    /* days */diff[0] = (diffInSeconds = (diffInSeconds / 24));

    System.out.println(String.format(
        "%d day%s, %d hour%s, %d minute%s, %d second%s ago",
        diff[0],
        diff[0] > 1 ? "s" : "",
        diff[1],
        diff[1] > 1 ? "s" : "",
        diff[2],
        diff[2] > 1 ? "s" : "",
        diff[3],
        diff[3] > 1 ? "s" : ""));

Yup awakened the dead I have, but here's my improved implementation based on @mtim posted code, as this thread comes almost on top of the searches so I am messing with the sleepy hollow,

    public static String getFriendlyTime(Date dateTime) {
    StringBuffer sb = new StringBuffer();
    Date current = Calendar.getInstance().getTime();
    long diffInSeconds = (current.getTime() - dateTime.getTime()) / 1000;

    /*long diff[] = new long[]{0, 0, 0, 0};
    /* sec *  diff[3] = (diffInSeconds >= 60 ? diffInSeconds % 60 : diffInSeconds);
    /* min *  diff[2] = (diffInSeconds = (diffInSeconds / 60)) >= 60 ? diffInSeconds % 60 : diffInSeconds;
    /* hours *  diff[1] = (diffInSeconds = (diffInSeconds / 60)) >= 24 ? diffInSeconds % 24 : diffInSeconds;
    /* days * diff[0] = (diffInSeconds = (diffInSeconds / 24));
     */
    long sec = (diffInSeconds >= 60 ? diffInSeconds % 60 : diffInSeconds);
    long min = (diffInSeconds = (diffInSeconds / 60)) >= 60 ? diffInSeconds % 60 : diffInSeconds;
    long hrs = (diffInSeconds = (diffInSeconds / 60)) >= 24 ? diffInSeconds % 24 : diffInSeconds;
    long days = (diffInSeconds = (diffInSeconds / 24)) >= 30 ? diffInSeconds % 30 : diffInSeconds;
    long months = (diffInSeconds = (diffInSeconds / 30)) >= 12 ? diffInSeconds % 12 : diffInSeconds;
    long years = (diffInSeconds = (diffInSeconds / 12));

    if (years > 0) {
        if (years == 1) {
            sb.append("a year");
        } else {
            sb.append(years + " years");
        }
        if (years <= 6 && months > 0) {
            if (months == 1) {
                sb.append(" and a month");
            } else {
                sb.append(" and " + months + " months");
            }
        }
    } else if (months > 0) {
        if (months == 1) {
            sb.append("a month");
        } else {
            sb.append(months + " months");
        }
        if (months <= 6 && days > 0) {
            if (days == 1) {
                sb.append(" and a day");
            } else {
                sb.append(" and " + days + " days");
            }
        }
    } else if (days > 0) {
        if (days == 1) {
            sb.append("a day");
        } else {
            sb.append(days + " days");
        }
        if (days <= 3 && hrs > 0) {
            if (hrs == 1) {
                sb.append(" and an hour");
            } else {
                sb.append(" and " + hrs + " hours");
            }
        }
    } else if (hrs > 0) {
        if (hrs == 1) {
            sb.append("an hour");
        } else {
            sb.append(hrs + " hours");
        }
        if (min > 1) {
            sb.append(" and " + min + " minutes");
        }
    } else if (min > 0) {
        if (min == 1) {
            sb.append("a minute");
        } else {
            sb.append(min + " minutes");
        }
        if (sec > 1) {
            sb.append(" and " + sec + " seconds");
        }
    } else {
        if (sec <= 1) {
            sb.append("about a second");
        } else {
            sb.append("about " + sec + " seconds");
        }
    }

    sb.append(" ago");


    /*String result = new String(String.format(
    "%d day%s, %d hour%s, %d minute%s, %d second%s ago",
    diff[0],
    diff[0] > 1 ? "s" : "",
    diff[1],
    diff[1] > 1 ? "s" : "",
    diff[2],
    diff[2] > 1 ? "s" : "",
    diff[3],
    diff[3] > 1 ? "s" : ""));*/
    return sb.toString();
}

It obviously can be improved. basically it tries to get the time span more friendly, there are a few limitation though i.e. it would behave strangely if the time passed (parameter) is in future, and its limited up to the days, hours and seconds only (months and years not handled, so that someone else can ;-).

sample outputs are:

• about a second ago
• 8 minutes and 34 seconds ago
• an hour and 4 minutes ago
• a day ago
• 29 days ago
• a year and 3 months ago

, cheers :D

EDIT: now supports months and years :P

I'd recommend you have a look at HumanTime