Cnnvert DateTime to --ago format

TimeUtils.java

/*
 * Copyright 2014 Google Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


import android.content.Context;
import android.text.TextUtils;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

public class TimeUtils {
    private static final int SECOND = 1000;
    private static final int MINUTE = 60 * SECOND;
    private static final int HOUR = 60 * MINUTE;
    private static final int DAY = 24 * HOUR;

    public static String getTimeAgo(Context ctx, Date date) {
        // TODO: use DateUtils methods instead
        long time;

        Calendar timeCal = Calendar.getInstance();
        timeCal.setTime(date);

        Calendar currentCal = Calendar.getInstance();
        currentCal.setTime(new Date());

//        long now = System.currentTimeMillis();
        time = timeCal.getTimeInMillis();
        long now = currentCal.getTimeInMillis();
        if (time > now || time <= 0) {
            return null;
        }

        final long diff = now - time;
        if (diff < MINUTE) {
            return "just now";
        } else if (diff < 2 * MINUTE) {
            return "a minute ago";
        } else if (diff < 50 * MINUTE) {
            return diff / MINUTE + " minutes ago";
        } else if (diff < 90 * MINUTE) {
            return "an hour ago";
        } else if (diff < 24 * HOUR) {
            return diff / HOUR + " hours ago";
        } else if (diff < 48 * HOUR) {
            return "yesterday";
        } else {
            return diff / DAY + " days ago";
        }
    }

    private static final SimpleDateFormat[] ACCEPTED_TIMESTAMP_FORMATS = {
            new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss Z", Locale.US),
            new SimpleDateFormat("EEE MMM dd HH:mm:ss yyyy", Locale.US),
            new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.US),
            new SimpleDateFormat("yyyy-MM-dd HH:mm:ss Z", Locale.US),
            new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ", Locale.US),
            new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.US),
            new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss Z", Locale.US)
    };

    private static final SimpleDateFormat VALID_IFMODIFIEDSINCE_FORMAT =
            new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss Z", Locale.US);

    public static Date parseTimestamp(String timestamp) {
        for (SimpleDateFormat format : ACCEPTED_TIMESTAMP_FORMATS) {
            format.setTimeZone(TimeZone.getTimeZone("GMT"));
            try {
                return format.parse(timestamp);
            } catch (ParseException ex) {
                continue;
            }
        }

        // All attempts to parse have failed
        return null;
    }

    public static boolean isValidFormatForIfModifiedSinceHeader(String timestamp) {
        try {
            return VALID_IFMODIFIEDSINCE_FORMAT.parse(timestamp) != null;
        } catch (Exception ex) {
            return false;
        }
    }

    public static long timestampToMillis(String timestamp, long defaultValue) {
        if (TextUtils.isEmpty(timestamp)) {
            return defaultValue;
        }
        Date d = parseTimestamp(timestamp);
        return d == null ? defaultValue : d.getTime();
    }

}